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Accogli A, Park YN, Lenk GM, Severino M, Scala M, Denecke J, Hempel M, Lessel D, Kortüm F, Salpietro V, de Marco P, Guerrisi S, Torella A, Nigro V, Srour M, Turro E, Labarque V, Freson K, Piatelli G, Capra V, Kitzman JO, Meisler MH. Biallelic loss-of-function variants of SLC12A9 cause lysosome dysfunction and a syndromic neurodevelopmental disorder. Genet Med 2024; 26:101097. [PMID: 38334070 DOI: 10.1016/j.gim.2024.101097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 01/31/2024] [Accepted: 02/01/2024] [Indexed: 02/10/2024] Open
Abstract
PURPOSE Pathogenic variants of FIG4 generate enlarged lysosomes and neurological and developmental disorders. To identify additional genes regulating lysosomal volume, we carried out a genome-wide activation screen to detect suppression of enlarged lysosomes in FIG4-/- cells. METHODS The CRISPR-a gene activation screen utilized sgRNAs from the promoters of protein-coding genes. Fluorescence-activated cell sorting separated cells with correction of the enlarged lysosomes from uncorrected cells. Patient variants of SLC12A9 were identified by exome or genome sequencing and studied by segregation analysis and clinical characterization. RESULTS Overexpression of SLC12A9, a solute co-transporter, corrected lysosomal swelling in FIG4-/- cells. SLC12A9 (NP_064631.2) colocalized with LAMP2 at the lysosome membrane. Biallelic variants of SLC12A9 were identified in 3 unrelated probands with neurodevelopmental disorders. Common features included intellectual disability, skeletal and brain structural abnormalities, congenital heart defects, and hypopigmented hair. Patient 1 was homozygous for nonsense variant p.(Arg615∗), patient 2 was compound heterozygous for p.(Ser109Lysfs∗20) and a large deletion, and proband 3 was compound heterozygous for p.(Glu290Glyfs∗36) and p.(Asn552Lys). Fibroblasts from proband 1 contained enlarged lysosomes that were corrected by wild-type SLC12A9 cDNA. Patient variant p.(Asn552Lys) failed to correct the lysosomal defect. CONCLUSION Impaired function of SLC12A9 results in enlarged lysosomes and a recessive disorder with a recognizable neurodevelopmental phenotype.
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Affiliation(s)
- Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Centre (MUHC), Montreal, QC, Canada; Department of Human Genetics, McGill University, Montreal, QC, Canada
| | - Young N Park
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | | | - Marcello Scala
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Università Degli Studi di Genova, Genoa, Italy; Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Jonas Denecke
- University Children's Hospital, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Maja Hempel
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Davor Lessel
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Fanny Kortüm
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Vincenzo Salpietro
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, United Kingdom; Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, 67100, L'Aquila, Italy
| | | | | | - Annalaura Torella
- Telethon Institute of Genetics and Medicine (TIGEM), Naples, Italy; Department of Precision Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Vincenzo Nigro
- Telethon Institute of Genetics and Medicine (TIGEM), Naples, Italy; Department of Precision Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Myriam Srour
- Department of Human Genetics, McGill University, Montreal, QC, Canada; Department of Pediatrics, Division of Pediatric Neurology, McGill University, Montreal, QC, Canada; McGill University Health Center (MUHC) Research Institute, Montreal, QC, Canada; Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Ernest Turro
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY; Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY; Charles Bronfman Institute for Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Veerle Labarque
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium; Paediatric Hemato-Oncology, University Hospitals Leuven, Leuven, Belgium
| | - Kathleen Freson
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Gianluca Piatelli
- Department of Neurosurgery, Gaslini Children's Hospital, Genoa, Italy
| | - Valeria Capra
- Genomics and Clinical Genetics, IRCCS Instituto G. Gaslini, Genoa, Italy
| | - Jacob O Kitzman
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI.
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Hill SF, Yu W, Ziobro J, Chalasani S, Reger F, Meisler MH. Long-Term Downregulation of the Sodium Channel Gene Scn8a Is Therapeutic in Mouse Models of SCN8A Epilepsy. Ann Neurol 2024; 95:754-759. [PMID: 38113311 DOI: 10.1002/ana.26861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 11/06/2023] [Accepted: 12/14/2023] [Indexed: 12/21/2023]
Abstract
OBJECTIVE De novo mutations of the voltage-gated sodium channel gene SCN8A cause developmental and epileptic encephalopathy (DEE). Most pathogenic variants result in gain-of-function changes in activity of the sodium channel Nav1.6, poorly controlled seizures, and significant comorbidities. In previous work, an antisense oligonucleotide (ASO) reduced Scn8a transcripts and increased lifespan after neonatal administration to a mouse model. Here, we tested long-term ASO treatment initiated after seizure onset, as required for clinical application. METHODS ASO treatment was initiated after observation of a convulsive seizure and repeated at 4 to 6 week intervals for 1 year. We also tested the long-term efficacy of an AAV10-short hairpin RNA (shRNA) virus administered on P1. RESULTS Repeated treatment with the Scn8a ASO initiated after seizure onset provided long-term survival and reduced seizure frequency during a 12 month observation period. A single treatment with viral shRNA was also protective during 12 months of observation. INTERPRETATION Downregulation of Scn8a expression that is initiated after the onset of seizures is effective for long-term treatment in a model of SCN8A-DEE. Repeated ASO administration or a single dose of viral shRNA prevented seizures and extended survival through 12 months of observation. ANN NEUROL 2024;95:754-759.
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Affiliation(s)
- Sophie F Hill
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Julie Ziobro
- Department of Pediatrics, University of Michigan, Ann Arbor, MI
| | - Sanjna Chalasani
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Faith Reger
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Miriam H Meisler
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
- Department of Neurology, University of Michigan, Ann Arbor, MI
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3
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Meyer-Schuman R, Cale AR, Pierluissi JA, Jonatzke KE, Park YN, Lenk GM, Oprescu SN, Grachtchouk MA, Dlugosz AA, Beg AA, Meisler MH, Antonellis A. Predictive modeling provides insight into the clinical heterogeneity associated with TARS1 loss-of-function mutations. bioRxiv 2024:2024.03.25.586600. [PMID: 38585737 PMCID: PMC10996635 DOI: 10.1101/2024.03.25.586600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Aminoacyl-tRNA synthetases (ARSs) are ubiquitously expressed, essential enzymes that complete the first step of protein translation: ligation of amino acids to cognate tRNAs. Genes encoding ARSs have been implicated in myriad dominant and recessive phenotypes, the latter often affecting multiple tissues but with frequent involvement of the central and peripheral nervous system, liver, and lungs. Threonyl-tRNA synthetase (TARS1) encodes the enzyme that ligates threonine to tRNATHR in the cytoplasm. To date, TARS1 variants have been implicated in a recessive brittle hair phenotype. To better understand TARS1-related recessive phenotypes, we engineered three TARS1 missense mutations predicted to cause a loss-of-function effect and studied these variants in yeast and worm models. This revealed two loss-of-function mutations, including one hypomorphic allele (R433H). We next used R433H to study the effects of partial loss of TARS1 function in a compound heterozygous mouse model (R433H/null). This model presents with phenotypes reminiscent of patients with TARS1 variants and with distinct lung and skin defects. This study expands the potential clinical heterogeneity of TARS1-related recessive disease, which should guide future clinical and genetic evaluations of patient populations.
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Affiliation(s)
| | - Allison R. Cale
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Kira E. Jonatzke
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Young N. Park
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Guy M. Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | | | | | - Andrzej A. Dlugosz
- Department of Dermatology, University of Michigan, Ann Arbor, MI, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Asim A. Beg
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Miriam H. Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Anthony Antonellis
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
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Hill SF, Jafar-Nejad P, Rigo F, Meisler MH. Reduction of Kcnt1 is therapeutic in mouse models of SCN1A and SCN8A epilepsy. Front Neurosci 2023; 17:1282201. [PMID: 37901435 PMCID: PMC10603267 DOI: 10.3389/fnins.2023.1282201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 09/25/2023] [Indexed: 10/31/2023] Open
Abstract
Developmental and epileptic encephalopathies (DEEs) are severe seizure disorders with inadequate treatment options. Gain- or loss-of-function mutations of neuronal ion channel genes, including potassium channels and voltage-gated sodium channels, are common causes of DEE. We previously demonstrated that reduced expression of the sodium channel gene Scn8a is therapeutic in mouse models of sodium and potassium channel mutations. In the current study, we tested whether reducing expression of the potassium channel gene Kcnt1 would be therapeutic in mice with mutation of the sodium channel genes Scn1a or Scn8a. A Kcnt1 antisense oligonucleotide (ASO) prolonged survival of both Scn1a and Scn8a mutant mice, suggesting a modulatory effect for KCNT1 on the balance between excitation and inhibition. The cation channel blocker quinidine was not effective in prolonging survival of the Scn8a mutant. Our results implicate KCNT1 as a therapeutic target for treatment of SCN1A and SCN8A epilepsy.
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Affiliation(s)
- Sophie F. Hill
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, United States
| | | | - Frank Rigo
- Ionis Pharmaceuticals, Carlsbad, CA, United States
| | - Miriam H. Meisler
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, United States
- Department of Neurology, University of Michigan, Ann Arbor, MI, United States
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5
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Cao X, Lenk GM, Meisler MH. Altered phenotypes due to genetic interaction between the mouse phosphoinositide biosynthesis genes Fig4 and Pip4k2c. G3 (Bethesda) 2023; 13:jkad007. [PMID: 36691351 PMCID: PMC10411592 DOI: 10.1093/g3journal/jkad007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/02/2023] [Indexed: 01/25/2023]
Abstract
Loss-of-function mutations of FIG4 are responsible for neurological disorders in human and mouse that result from reduced abundance of the signaling lipid PI(3,5)P2. In contrast, loss-of-function mutations of the phosphoinositide kinase PIP4K2C result in elevated abundance of PI(3,5)P2. These opposing effects on PI(3,5)P2 suggested that we might be able to compensate for deficiency of FIG4 by reducing expression of PIP4K2C. To test this hypothesis in a whole animal model, we generated triallelic mice with genotype Fig 4-/-, Pip4k2c+/-; these mice are null for Fig 4 and haploinsufficient for Pip4k2c. The neonatal lethality of Fig 4 null mice in the C57BL/6J strain background was rescued by reduced expression of Pip4k2c. The lysosome enlargement characteristic of Fig 4 null cells was also reduced by heterozygous loss of Pip4k2c. The data demonstrate interaction between these two genes, and suggest that inhibition of the kinase PIPK4C2 could be a target for treatment of FIG4 deficiency disorders such as Charcot-Marie-Tooth Type 4J and Yunis-Varón Syndrome.
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Affiliation(s)
- Xu Cao
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
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6
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Cao X, Lenk GM, Mikusevic V, Mindell JA, Meisler MH. The chloride antiporter CLCN7 is a modifier of lysosome dysfunction in FIG 4 and VAC14 mutants. PLoS Genet 2023; 19:e1010800. [PMID: 37363915 DOI: 10.1371/journal.pgen.1010800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 05/26/2023] [Indexed: 06/28/2023] Open
Abstract
The phosphatase FIG 4 and the scaffold protein VAC14 function in the biosynthesis of PI(3,5)P2, a signaling lipid that inhibits the lysosomal chloride transporter ClC-7. Loss-of-function mutations of FIG 4 and VAC14 reduce PI(3,5)P2 and result in lysosomal disorders characterized by accumulation of enlarged lysosomes and neurodegeneration. Similarly, a gain of function mutation of CLCN7 encoding ClC-7 also results in enlarged lysosomes. We therefore tested the ability of reduced CLCN7 expression to compensate for loss of FIG 4 or VAC14. Knock-out of CLCN7 corrected lysosomal swelling and partially corrected lysosomal hyperacidification in FIG 4 null cell cultures. Knockout of the related transporter CLCN6 (ClC-6) in FIG 4 null cells did not affect the lysosome phenotype. In the Fig 4 null mouse, reduction of ClC-7 by expression of the dominant negative CLCN7 variant p.Gly215Arg improved growth and neurological function and increased lifespan by 20%. These observations demonstrate a role for the CLCN7 chloride transporter in pathogenesis of FIG 4 and VAC14 disorders. Reduction of CLCN7 provides a new target for treatment of FIG 4 and VAC14 deficiencies that lack specific therapies, such as Charcot-Marie-Tooth Type 4J and Yunis-Varón syndrome.
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Affiliation(s)
- Xu Cao
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Vedrana Mikusevic
- Membrane Transport Biophysics Section, National Institutes of Neurological Disorders and Stroke, Bethesda, Maryland, United States of America
| | - Joseph A Mindell
- Membrane Transport Biophysics Section, National Institutes of Neurological Disorders and Stroke, Bethesda, Maryland, United States of America
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
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7
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Lenk GM, Meisler MH. Chloroquine corrects enlarged lysosomes in FIG4 null cells and reduces neurodegeneration in Fig4 null mice. Mol Genet Metab 2022; 137:382-387. [PMID: 36434903 PMCID: PMC10364190 DOI: 10.1016/j.ymgme.2022.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022]
Abstract
Loss-of-function mutations of FIG4 impair the biosynthesis of PI(3,5)P2 and are responsible for rare genetic disorders including Yunis-Varón Syndrome and Charcot-Marie-Tooth Disease Type 4 J. Cultured cells deficient in FIG4 accumulate enlarged lysosomes with hyperacidic pH, due in part to impaired regulation of lysosomal ion channels and elevated intra-lysosomal osmotic pressure. We evaluated the effects of the FDA approved drug chloroquine, which is known to reduce lysosome acidity, on FIG4 deficient cell culture and on a mouse model. Chloroquine corrected the enlarged lysosomes in FIG4 null cells. In null mice, addition of chloroquine to the drinking water slowed progression of the disorder. Growth and mobility were dramatically improved during the first month of life, and spongiform degeneration of the nervous system was reduced. The median survival of Fig4 null mice was increased from 4 weeks for untreated mutants to 8 weeks with chloroquine treatment (p < 0.009). Chloroquine thus corrects the lysosomal swelling in cultured cells and ameliorates Fig4 deficiency in vivo. The improved phenotype of mice with complete loss of Fig4 suggests that chloroquine could be beneficial FIG2 in partial loss-of-function disorders such as Charcot-Marie-Tooth Type 4 J.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, United States of America.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, United States of America; Department of Neurology, University of Michigan, Ann Arbor, MI 48109, United States of America
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8
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Hill SF, Ziobro JM, Jafar‐Nejad P, Rigo F, Meisler MH. Genetic interaction between Scn8a and potassium channel genes Kcna1 and Kcnq2. Epilepsia 2022; 63:e125-e131. [PMID: 35892317 PMCID: PMC9804156 DOI: 10.1111/epi.17374] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/24/2022] [Accepted: 07/25/2022] [Indexed: 01/07/2023]
Abstract
Voltage-gated sodium and potassium channels regulate the initiation and termination of neuronal action potentials. Gain-of-function mutations of sodium channel Scn8a and loss-of-function mutations of potassium channels Kcna1 and Kcnq2 increase neuronal activity and lead to seizure disorders. We tested the hypothesis that reducing the expression of Scn8a would compensate for loss-of-function mutations of Kcna1 or Kcnq2. Scn8a expression was reduced by the administration of an antisense oligonucleotide (ASO). This treatment lengthened the survival of the Kcn1a and Kcnq2 mutants, and reduced the seizure frequency in the Kcnq2 mutant mice. These observations suggest that reduction of SCN8A may be therapeutic for genetic epilepsies resulting from mutations in these potassium channel genes.
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Affiliation(s)
- Sophie F. Hill
- Neuroscience Graduate ProgramUniversity of MichiganAnn ArborMichiganUSA,Department of Human GeneticsUniversity of MichiganAnn ArborMichiganUSA
| | - Julie M. Ziobro
- Department of PediatricsUniversity of MichiganAnn ArborMichiganUSA
| | | | - Frank Rigo
- Ionis PharmaceuticalsCarlsbadCaliforniaUSA
| | - Miriam H. Meisler
- Neuroscience Graduate ProgramUniversity of MichiganAnn ArborMichiganUSA,Department of Human GeneticsUniversity of MichiganAnn ArborMichiganUSA,Department of NeurologyUniversity of MichiganAnn ArborMichiganUSA
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9
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Yu W, Mulligan MK, Williams RW, Meisler MH. Correction of the hypomorphic Gabra2 splice site variant in mouse strain C57BL/6J modifies the severity of Scn8a encephalopathy. HGG Adv 2022; 3:100064. [PMID: 35047853 PMCID: PMC8756487 DOI: 10.1016/j.xhgg.2021.100064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/30/2021] [Indexed: 10/31/2022] Open
Abstract
De novo gain-of-function mutations of SCN8A are a significant cause of developmental and epileptic encephalopathy (DEE) (MIM: 614558). The severely affected individuals exhibit refractory seizures, developmental delay, and cognitive disabilities, often accompanied by impaired movement. Individuals with the identical SCN8A variant often differ in clinical course, suggesting a role for modifier genes in disease severity. In a previous study we demonstrated genetic linkage between a hypomorphic mutation in the Gabra2 gene and seizure severity in a mouse model of the human SCN8A pathogenic variant p.Arg1872Trp. Homozygosity for the hypomorphic Gabra2 mutation was associated with early seizure onset and shortened lifespan. We have now confirmed Gabra2 as the modifier gene using a knock-in allele that corrects the splice site variant in strain C57BL/6J. Correction of the Gabra2 variant restores transcript abundance, increases the age of seizure onset, and extends survival of the Scn8a mutant mice. GABRA2 encodes the α2 subunit of the GABAA receptor that provides inhibitory input to dendrites and the the axon initial segment of excitatory neurons. Quantitative variation in human GABAA receptor expression could contribute to variation in the severity of genetic epilepsies and suggests a potential therapeutic intervention.
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Affiliation(s)
- Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Megan K Mulligan
- Department of Genetics, Genomics, and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38103, USA
| | - Robert W Williams
- Department of Genetics, Genomics, and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38103, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109, USA
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10
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Yang X, Yin H, Wang X, Sun Y, Bian X, Zhang G, Li A, Cao A, Li B, Ebrahimi-Fakhari D, Yang Z, Meisler MH, Liu Q. Social Deficits and Cerebellar Degeneration in Purkinje Cell Scn8a Knockout Mice. Front Mol Neurosci 2022; 15:822129. [PMID: 35557557 PMCID: PMC9087741 DOI: 10.3389/fnmol.2022.822129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/18/2022] [Indexed: 11/23/2022] Open
Abstract
Mutations in the SCN8A gene encoding the voltage-gated sodium channel α-subunit Nav1. 6 have been reported in individuals with epilepsy, intellectual disability and features of autism spectrum disorder. SCN8A is widely expressed in the central nervous system, including the cerebellum. Cerebellar dysfunction has been implicated in autism spectrum disorder. We investigated conditional Scn8a knockout mice under C57BL/6J strain background that specifically lack Scn8a expression in cerebellar Purkinje cells (Scn8a flox/flox , L7Cre + mice). Cerebellar morphology was analyzed by immunohistochemistry and MR imaging. Mice were subjected to a battery of behavioral tests including the accelerating rotarod, open field, elevated plus maze, light-dark transition box, three chambers, male-female interaction, social olfaction, and water T-maze tests. Patch clamp recordings were used to evaluate evoked action potentials in Purkinje cells. Behavioral phenotyping demonstrated that Scn8a flox/flox , L7Cre + mice have impaired social interaction, motor learning and reversal learning as well as increased repetitive behavior and anxiety-like behaviors. By 5 months of age, Scn8a flox/flox , L7Cre + mice began to exhibit cerebellar Purkinje cell loss and reduced molecular thickness. At 9 months of age, Scn8a flox/flox , L7Cre + mice exhibited decreased cerebellar size and a reduced number of cerebellar Purkinje cells more profoundly, with evidence of additional neurodegeneration in the molecular layer and deep cerebellar nuclei. Purkinje cells in Scn8a flox/flox , L7Cre + mice exhibited reduced repetitive firing. Taken together, our experiments indicated that loss of Scn8a expression in cerebellar Purkinje cells leads to cerebellar degeneration and several ASD-related behaviors. Our study demonstrated the specific contribution of loss of Scn8a in cerebellar Purkinje cells to behavioral deficits characteristic of ASD. However, it should be noted that our observed effects reported here are specific to the C57BL/6 genome type.
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Affiliation(s)
- Xiaofan Yang
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, China.,Key Laboratory of Experimental Teratology, Ministry of Education, Department of Genetics, School of Basic Medical Sciences, Shandong University, Jinan, China
| | - Hongqiang Yin
- Medical School, State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials for Ministry of Education, Nankai University, Tianjin, China.,Department of Operational Medicine, Tianjin Institute of Environmental & Operational Medicine, Tianjin, China
| | - Xiaojing Wang
- Key Laboratory of Experimental Teratology, Ministry of Education, Department of Genetics, School of Basic Medical Sciences, Shandong University, Jinan, China
| | - Yueqing Sun
- Key Laboratory of Experimental Teratology, Ministry of Education, Department of Genetics, School of Basic Medical Sciences, Shandong University, Jinan, China
| | - Xianli Bian
- Department of Neurology, Second Hospital of Shandong University, Jinan, China
| | - Gaorui Zhang
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, China
| | - Anning Li
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, China
| | - Aihua Cao
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, China
| | - Baomin Li
- Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, China
| | - Darius Ebrahimi-Fakhari
- Department of Neurology, The F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Zhuo Yang
- Medical School, State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials for Ministry of Education, Nankai University, Tianjin, China
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, United States.,Department of Neurology, University of Michigan, Ann Arbor, MI, United States
| | - Qiji Liu
- Key Laboratory of Experimental Teratology, Ministry of Education, Department of Genetics, School of Basic Medical Sciences, Shandong University, Jinan, China.,Key Laboratory of Birth Regulation and Control Technology of National Health Commission of China, Maternal and Child Health Care Hospital of Shandong Province, Jinan, China
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11
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Abstract
Antisense oligonucleotides (ASOs) are short oligonucleotides that can modify gene expression and mRNA splicing in the nervous system. The FDA has approved ASOs for treatment of ten genetic disorders, with many applications currently in the pipeline. We describe the molecular mechanisms of ASO treatment for four neurodevelopmental and neuromuscular disorders. The ASO nusinersen is a general treatment for mutations of SMN1 in spinal muscular atrophy that corrects the splicing defect in the SMN2 gene. Milasen is a patient-specific ASO that rescues splicing of CNL7 in Batten's disease. STK-001 is an ASO that increases expression of the sodium channel gene SCN1A by exclusion of a poison exon. An ASO that reduces the abundance of the SCN8A mRNA is therapeutic in mouse models of developmental and epileptic encephalopathy. These examples demonstrate the variety of mechanisms and range of applications of ASOs for treatment of neurodevelopmental disorders.
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Affiliation(s)
- Sophie F Hill
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Miriam H Meisler
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
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12
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Yu W, Smolen CE, Hill SF, Meisler MH. Spontaneous seizures and elevated seizure susceptibility in response to somatic mutation of sodium channel Scn8a in the mouse. Hum Mol Genet 2021; 30:902-907. [PMID: 33822038 PMCID: PMC8165645 DOI: 10.1093/hmg/ddab092] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/24/2021] [Accepted: 03/29/2021] [Indexed: 02/05/2023] Open
Abstract
De novo mutations of neuronal sodium channels are responsible for ~5% of developmental and epileptic encephalopathies, but the role of somatic mutation of these genes in adult-onset epilepsy is not known. We evaluated the role of post-zygotic somatic mutation by adult activation of a conditional allele of the pathogenic variant Scn8aR1872W in the mouse. After activation of CAG-Cre-ER by tamoxifen, the mutant transcript was expressed throughout the brain at a level proportional to tamoxifen dose. The threshold for generation of spontaneous seizures was reached when the proportion of mutant transcript reached 8% of total Scn8a transcript, equivalent to expression of the epileptogenic variant in 16% of heterozygous neurons. Expression below this level did not result in spontaneous seizures, but did increase susceptibility to seizure induction by kainate or auditory stimulation. The relatively high threshold for spontaneous seizures indicates that somatic mutation of sodium channels is unlikely to contribute to the elevated incidence of epilepsy in the elderly population. However, somatic mutation could increase susceptibility to other seizure stimuli.
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Affiliation(s)
- Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109 USA
| | - Corrine E Smolen
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109 USA
| | - Sophie F Hill
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109 USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109 USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109 USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109 USA
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13
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Wenker IC, Teran FA, Wengert ER, Wagley PK, Panchal PS, Blizzard EA, Saraf P, Wagnon JL, Goodkin HP, Meisler MH, Richerson GB, Patel MK. Postictal Death Is Associated with Tonic Phase Apnea in a Mouse Model of Sudden Unexpected Death in Epilepsy. Ann Neurol 2021; 89:1023-1035. [PMID: 33604927 DOI: 10.1002/ana.26053] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 02/17/2021] [Accepted: 02/17/2021] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Sudden unexpected death in epilepsy (SUDEP) is an unpredictable and devastating comorbidity of epilepsy that is believed to be due to cardiorespiratory failure immediately after generalized convulsive seizures. METHODS We performed cardiorespiratory monitoring of seizure-induced death in mice carrying either a p.Arg1872Trp or p.Asn1768Asp mutation in a single Scn8a allele-mutations identified from patients who died from SUDEP-and of seizure-induced death in pentylenetetrazole-treated wild-type mice. RESULTS The primary cause of seizure-induced death for all mice was apnea, as (1) apnea began during a seizure and continued for tens of minutes until terminal asystole, and (2) death was prevented by mechanical ventilation. Fatal seizures always included a tonic phase that was coincident with apnea. This tonic phase apnea was not sufficient to produce death, as it also occurred during many nonfatal seizures; however, all seizures that were fatal had tonic phase apnea. We also made the novel observation that continuous tonic diaphragm contraction occurred during tonic phase apnea, which likely contributes to apnea by preventing exhalation, and this was only fatal when breathing did not resume after the tonic phase ended. Finally, recorded seizures from a patient with developmental epileptic encephalopathy with a previously undocumented SCN8A likely pathogenic variant (p.Leu257Val) revealed similarities to those of the mice, namely, an extended tonic phase that was accompanied by apnea. INTERPRETATION We conclude that apnea coincident with the tonic phase of a seizure, and subsequent failure to resume breathing, are the determining events that cause seizure-induced death in Scn8a mutant mice. ANN NEUROL 2021;89:1023-1035.
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Affiliation(s)
- Ian C Wenker
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA
| | - Frida A Teran
- Department of Neurology, University of Iowa, Iowa City, IA.,Medical Scientist Training Program, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA
| | - Eric R Wengert
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA.,Neuroscience Graduate Program, University of Virginia, Charlottesville, VA
| | - Pravin K Wagley
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA.,Department of Neurology, University of Virginia Health System, Charlottesville, VA
| | - Payal S Panchal
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA
| | - Elizabeth A Blizzard
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA
| | - Priyanka Saraf
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Howard P Goodkin
- Department of Neurology, University of Virginia Health System, Charlottesville, VA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - George B Richerson
- Department of Neurology, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA.,Veterans Affairs Medical Center, Iowa City, IA
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA
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14
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Yu W, Hill SF, Xenakis JG, Pardo-Manuel de Villena F, Wagnon JL, Meisler MH. Gabra2 is a genetic modifier of Scn8a encephalopathy in the mouse. Epilepsia 2020; 61:2847-2856. [PMID: 33140451 PMCID: PMC7756374 DOI: 10.1111/epi.16741] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 12/23/2022]
Abstract
Objective SCN8A encephalopathy is a developmental epileptic encephalopathy typically caused by de novo gain‐of‐function mutations in Nav1.6. Severely affected individuals exhibit refractory seizures, developmental delay, cognitive disabilities, movement disorders, and elevated risk of sudden death. Patients with the identical SCN8A variant can differ in clinical course, suggesting a role for modifier genes in determining disease severity. The identification of genetic modifiers contributes to understanding disease pathogenesis and suggesting therapeutic interventions. Methods We generated F1 and F2 crosses between inbred mouse strains and mice carrying the human pathogenic variants SCN8A‐R1872W and SCN8A‐N1768D. Quantitative trait locus (QTL) analysis of seizure‐related phenotypes was used for chromosomal mapping of modifier loci. Results In an F2 cross between strain SJL/J and C57BL/6J mice carrying the patient mutation R1872W, we identified a major QTL on chromosome 5 containing the Gabra2 gene. Strain C57BL/6J carries a splice site mutation that reduces expression of Gabra2, encoding the α2 subunit of the aminobutyric acid type A receptor. The protective wild‐type allele of Gabra2 from strain SJL/J delays the age at seizure onset and extends life span of the Scn8a mutant mice. Additional Scn8a modifiers were observed in the F2 cross and in an F1 cross with strain C3HeB/FeJ. Significance These studies demonstrate that the SJL/J strain carries multiple modifiers with protective effects against seizures induced by gain‐of‐function mutations in Scn8a. Homozygosity for the hypomorphic variant of Gabra2 in strain C57BL/6J is associated with early seizure onset and short life span. GABRA2 is a potential therapeutic target for SCN8A encephalopathy.
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Affiliation(s)
- Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Sophie F Hill
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - James G Xenakis
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
| | | | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
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15
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Abstract
De novo mutations of the neuronal sodium channel SCN8A have been identified in approximately 2% of individuals with epileptic encephalopathy. These missense mutations alter the biophysical properties of sodium channel Nav1.6 in ways that lead to neuronal hyperexcitability. We generated two mouse models carrying patient mutations N1768D and R1872W to examine the effects on neuronal function in vivo. The conditional R1872W mutation is activated by expression of CRE recombinase, permitting characterization of the effects of the mutation on different classes of neurons and at different points in postnatal development. Preclinical drug testing in these mouse models provides support for several new therapies for this devastating disorder. In contrast with the gain-of-function mutations in epilepsy, mutations of SCN8A that result in partial or complete loss of function are associated with intellectual disability and other disorders.
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Affiliation(s)
- Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
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16
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Lenk GM, Jafar-Nejad P, Hill SF, Huffman LD, Smolen CE, Wagnon JL, Petit H, Yu W, Ziobro J, Bhatia K, Parent J, Giger RJ, Rigo F, Meisler MH. Scn8a Antisense Oligonucleotide Is Protective in Mouse Models of SCN8A Encephalopathy and Dravet Syndrome. Ann Neurol 2020; 87:339-346. [PMID: 31943325 PMCID: PMC7064908 DOI: 10.1002/ana.25676] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/07/2020] [Accepted: 01/07/2020] [Indexed: 12/19/2022]
Abstract
Objective SCN8A encephalopathy is a developmental and epileptic encephalopathy (DEE) caused by de novo gain‐of‐function mutations of sodium channel Nav1.6 that result in neuronal hyperactivity. Affected individuals exhibit early onset drug‐resistant seizures, developmental delay, and cognitive impairment. This study was carried out to determine whether reducing the abundance of the Scn8a transcript with an antisense oligonucleotide (ASO) would delay seizure onset and prolong survival in a mouse model of SCN8A encephalopathy. Methods ASO treatment was tested in a conditional mouse model with Cre‐dependent expression of the pathogenic patient SCN8A mutation p.Arg1872Trp (R1872W). This model exhibits early onset of seizures, rapid progression, and 100% penetrance. An Scn1a+/− haploinsufficient mouse model of Dravet syndrome was also treated. ASO was administered by intracerebroventricular injection at postnatal day 2, followed in some cases by stereotactic injection at postnatal day 30. Results We observed a dose‐dependent increase in length of survival from 15 to 65 days in the Scn8a‐R1872W/+ mice treated with ASO. Electroencephalographic recordings were normal prior to seizure onset. Weight gain and activity in an open field were unaffected, but treated mice were less active in a wheel running assay. A single treatment with Scn8a ASO extended survival of Dravet syndrome mice from 3 weeks to >5 months. Interpretation Reduction of Scn8a transcript by 25 to 50% delayed seizure onset and lethality in mouse models of SCN8A encephalopathy and Dravet syndrome. Reduction of SCN8A transcript is a promising approach to treatment of intractable childhood epilepsies. Ann Neurol 2020;87:339–346
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | | | - Sophie F Hill
- Department of Human Genetics, University of Michigan, Ann Arbor, MI.,Neuroscience Program, Ann Arbor, MI
| | - Lucas D Huffman
- Neuroscience Program, Ann Arbor, MI.,Department of Cell and Developmental Biology, Ann Arbor, MI
| | - Corrine E Smolen
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Hayley Petit
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI
| | - Julie Ziobro
- Department of Neurology, University of Michigan, Ann Arbor, MI
| | - Kritika Bhatia
- Department of Neurology, University of Michigan, Ann Arbor, MI
| | - Jack Parent
- Department of Neurology, University of Michigan, Ann Arbor, MI
| | - Roman J Giger
- Neuroscience Program, Ann Arbor, MI.,Department of Cell and Developmental Biology, Ann Arbor, MI.,Department of Neurology, University of Michigan, Ann Arbor, MI
| | | | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI.,Neuroscience Program, Ann Arbor, MI.,Department of Neurology, University of Michigan, Ann Arbor, MI
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17
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Wengert ER, Tronhjem CE, Wagnon JL, Johannesen KM, Petit H, Krey I, Saga AU, Panchal PS, Strohm SM, Lange J, Kamphausen SB, Rubboli G, Lemke JR, Gardella E, Patel MK, Meisler MH, Møller RS. Biallelic inherited SCN8A variants, a rare cause of SCN8A-related developmental and epileptic encephalopathy. Epilepsia 2019; 60:2277-2285. [PMID: 31625145 DOI: 10.1111/epi.16371] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 09/24/2019] [Accepted: 09/24/2019] [Indexed: 01/01/2023]
Abstract
OBJECTIVE Monoallelic de novo gain-of-function variants in the voltage-gated sodium channel SCN8A are one of the recurrent causes of severe developmental and epileptic encephalopathy (DEE). In addition, a small number of de novo or inherited monoallelic loss-of-function variants have been found in patients with intellectual disability, autism spectrum disorder, or movement disorders. Inherited monoallelic variants causing either gain or loss-of-function are also associated with less severe conditions such as benign familial infantile seizures and isolated movement disorders. In all three categories, the affected individuals are heterozygous for a SCN8A variant in combination with a wild-type allele. In the present study, we describe two unusual families with severely affected individuals who inherited biallelic variants of SCN8A. METHODS We identified two families with biallelic SCN8A variants by diagnostic gene panel sequencing. Functional analysis of the variants was performed using voltage clamp recordings from transfected ND7/23 cells. RESULTS We identified three probands from two unrelated families with DEE due to biallelic SCN8A variants. Each parent of an affected individual carried a single heterozygous SCN8A variant and exhibited mild cognitive impairment without seizures. In both families, functional analysis demonstrated segregation of one allele with complete loss-of-function, and one allele with altered biophysical properties consistent with partial loss-of-function. SIGNIFICANCE These studies demonstrate that SCN8A DEE may, in rare cases, result from inheritance of two variants, both of which exhibit reduced channel activity. In these families, heterozygosity for the dominant variants results in less severe disease than biallelic inheritance of two variant alleles. The clinical consequences of variants with partial and complete loss of SCN8A function are variable and likely to be influenced by genetic background.
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Affiliation(s)
- Eric R Wengert
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Cathrine E Tronhjem
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan.,Department of Neuroscience, Ohio State University, Columbus, Ohio
| | - Katrine M Johannesen
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Hayley Petit
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
| | - Ilona Krey
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | - Anusha U Saga
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia
| | - Payal S Panchal
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia
| | - Samantha M Strohm
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia
| | - Jörn Lange
- Epilepsy Center Berlin-Brandenburg, Berlin, Germany
| | | | - Guido Rubboli
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark.,University of Copenhagen, Copenhagen, Denmark
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
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18
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Bunton-Stasyshyn RKA, Wagnon JL, Wengert ER, Barker BS, Faulkner A, Wagley PK, Bhatia K, Jones JM, Maniaci MR, Parent JM, Goodkin HP, Patel MK, Meisler MH. Prominent role of forebrain excitatory neurons in SCN8A encephalopathy. Brain 2019; 142:362-375. [PMID: 30601941 DOI: 10.1093/brain/awy324] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/29/2018] [Indexed: 12/25/2022] Open
Abstract
De novo mutations of the sodium channel gene SCN8A result in an epileptic encephalopathy with refractory seizures, developmental delay, and elevated risk of sudden death. p.Arg1872Trp is a recurrent de novo SCN8A mutation reported in 14 unrelated individuals with epileptic encephalopathy that included seizure onset in the prenatal or infantile period and severe verbal and ambulatory comorbidities. The major biophysical effect of the mutation was previously shown to be impaired channel inactivation accompanied by increased current density. We have generated a conditional mouse mutation in which expression of this severe gain-of-function mutation is dependent upon Cre recombinase. Global activation of p.Arg1872Trp by EIIa-Cre resulted in convulsive seizures and lethality at 2 weeks of age. Neural activation of the p.Arg1872Trp mutation by Nestin-Cre also resulted in early onset seizures and death. Restriction of p.Arg1872Trp expression to excitatory neurons using Emx1-Cre recapitulated seizures and juvenile lethality between 1 and 2 months of age. In contrast, activation of p.Arg1872Trp in inhibitory neurons by Gad2-Cre or Dlx5/6-Cre did not induce seizures or overt neurological dysfunction. The sodium channel modulator GS967/Prax330 prolonged survival of mice with global expression of R1872W and also modulated the activity of the mutant channel in transfected cells. Activation of the p.Arg1872Trp mutation in adult mice was sufficient to generate seizures and death, indicating that successful therapy will require lifelong treatment. These findings provide insight into the pathogenic mechanism of this gain-of-function mutation of SCN8A and identify excitatory neurons as critical targets for therapeutic intervention.
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Affiliation(s)
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Eric R Wengert
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Bryan S Barker
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Alexa Faulkner
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Pravin K Wagley
- Department of Neurology, University of Virginia, Charlottesville VA, USA
| | - Kritika Bhatia
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Julie M Jones
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Marissa R Maniaci
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Jack M Parent
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Howard P Goodkin
- Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA.,Department of Neurology, University of Virginia, Charlottesville VA, USA
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
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19
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Lenk GM, Park YN, Lemons R, Flynn E, Plank M, Frei CM, Davis MJ, Gregorka B, Swanson JA, Meisler MH, Kitzman JO. CRISPR knockout screen implicates three genes in lysosome function. Sci Rep 2019; 9:9609. [PMID: 31270356 PMCID: PMC6610096 DOI: 10.1038/s41598-019-45939-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 06/20/2019] [Indexed: 12/28/2022] Open
Abstract
Defective biosynthesis of the phospholipid PI(3,5)P2 underlies neurological disorders characterized by cytoplasmic accumulation of large lysosome-derived vacuoles. To identify novel genetic causes of lysosomal vacuolization, we developed an assay for enlargement of the lysosome compartment that is amenable to cell sorting and pooled screens. We first demonstrated that the enlarged vacuoles that accumulate in fibroblasts lacking FIG4, a PI(3,5)P2 biosynthetic factor, have a hyperacidic pH compared to normal cells'. We then carried out a genome-wide knockout screen in human HAP1 cells for accumulation of acidic vesicles by FACS sorting. A pilot screen captured fifteen genes, including VAC14, a previously identified cause of endolysosomal vacuolization. Three genes not previously associated with lysosome dysfunction were selected to validate the screen: C10orf35, LRRC8A, and MARCH7. We analyzed two clonal knockout cell lines for each gene. All of the knockout lines contained enlarged acidic vesicles that were positive for LAMP2, confirming their endolysosomal origin. This assay will be useful in the future for functional evaluation of patient variants in these genes, and for a more extensive genome-wide screen for genes required for endolysosome function. This approach may also be adapted for drug screens to identify small molecules that rescue endolysosomal vacuolization.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA.
| | - Young N Park
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Rosemary Lemons
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Emma Flynn
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Margaret Plank
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Christen M Frei
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Michael J Davis
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Brian Gregorka
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Joel A Swanson
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA
| | - Jacob O Kitzman
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, 48109-5618, USA.
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20
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Bissig C, Croisé P, Heiligenstein X, Hurbain I, Lenk GM, Kaufman E, Sannerud R, Annaert W, Meisler MH, Weisman LS, Raposo G, van Niel G. Correction: The PIKfyve complex regulates the early melanosome homeostasis required for physiological amyloid formation (doi:10.1242/jcs.229500). J Cell Sci 2019; 132:132/6/jcs231746. [PMID: 30923131 DOI: 10.1242/jcs.231746] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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21
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Mironova YA, Lin JP, Kalinski AL, Huffman LD, Lenk GM, Havton LA, Meisler MH, Giger RJ. Protective role of the lipid phosphatase Fig4 in the adult nervous system. Hum Mol Genet 2019; 27:2443-2453. [PMID: 29688489 DOI: 10.1093/hmg/ddy145] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 04/16/2018] [Indexed: 12/11/2022] Open
Abstract
The signaling lipid phosphatidylinositol 3,5-bisphosphate, PI(3,5)P2, functions in vesicular trafficking through the endo-lysosomal compartment. Cellular levels of PI(3,5)P2 are regulated by an enzyme complex comprised of the kinase PIKFYVE, the phosphatase FIG4, and the scaffold protein VAC14. Mutations of human FIG4 cause inherited disorders including Charcot-Marie-Tooth disease type 4J, polymicrogyria with epilepsy, and Yunis-Varón syndrome. Constitutive Fig4-/- mice exhibit intention tremor, spongiform degeneration of neural tissue, hypomyelination, and juvenile lethality. To determine whether PI(3,5)P2 is required in the adult, we generated Fig4flox/-; CAG-creER mice and carried out tamoxifen-induced gene ablation. Global ablation in adulthood leads to wasting, tremor, and motor impairment. Death follows within 2 months of tamoxifen treatment, demonstrating a life-long requirement for Fig4. Histological examinations of the sciatic nerve revealed profound Wallerian degeneration of myelinated fibers, but not C-fiber axons in Remak bundles. In optic nerve sections, myelinated fibers appear morphologically intact and carry compound action potentials at normal velocity and amplitude. However, when iKO mice are challenged with a chemical white matter lesion, repair of damaged CNS myelin is significantly delayed, demonstrating a novel role for Fig4 in remyelination. Thus, in the adult PNS Fig4 is required to protect myelinated axons from Wallerian degeneration. In the adult CNS, Fig4 is dispensable for fiber stability and nerve conduction, but is required for the timely repair of damaged white matter. The greater vulnerability of the PNS to Fig4 deficiency in the mouse is consistent with clinical observations in patients with Charcot-Marie-Tooth disease.
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Affiliation(s)
- Yevgeniya A Mironova
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA.,Cellular and Molecular Biology Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jing-Ping Lin
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Ashley L Kalinski
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Lucas D Huffman
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA.,Interdepartmental Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Leif A Havton
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Miriam H Meisler
- Interdepartmental Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA.,Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Roman J Giger
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA.,Cellular and Molecular Biology Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA.,Interdepartmental Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, USA
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22
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Lenk GM, Berry IR, Stutterd CA, Blyth M, Green L, Vadlamani G, Warren D, Craven I, Fanjul-Fernandez M, Rodriguez-Casero V, Lockhart PJ, Vanderver A, Simons C, Gibb S, Sadedin S, White SM, Christodoulou J, Skibina O, Ruddle J, Tan TY, Leventer RJ, Livingston JH, Meisler MH. Cerebral hypomyelination associated with biallelic variants of FIG4. Hum Mutat 2019; 40:619-630. [PMID: 30740813 DOI: 10.1002/humu.23720] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 12/11/2018] [Accepted: 02/06/2019] [Indexed: 01/07/2023]
Abstract
The lipid phosphatase gene FIG4 is responsible for Yunis-Varón syndrome and Charcot-Marie-Tooth disease Type 4J, a peripheral neuropathy. We now describe four families with FIG4 variants and prominent abnormalities of central nervous system (CNS) white matter (leukoencephalopathy), with onset in early childhood, ranging from severe hypomyelination to mild undermyelination, in addition to peripheral neuropathy. Affected individuals inherited biallelic FIG4 variants from heterozygous parents. Cultured fibroblasts exhibit enlarged vacuoles characteristic of FIG4 dysfunction. Two unrelated families segregate the same G > A variant in the +1 position of intron 21 in the homozygous state in one family and compound heterozygous in the other. This mutation in the splice donor site of exon 21 results in read-through from exon 20 into intron 20 and truncation of the final 115 C-terminal amino acids of FIG4, with retention of partial function. The observed CNS white matter disorder in these families is consistent with the myelination defects in the FIG4 null mouse and the known role of FIG4 in oligodendrocyte maturation. The families described here the expanded clinical spectrum of FIG4 deficiency to include leukoencephalopathy.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
| | - Ian R Berry
- Leeds Genetics Laboratory, The Leeds Teaching Hospitals NHS Trust, St James's University Hospital, Leeds, UK
| | - Chloe A Stutterd
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Royal Children's Hospital, Melbourne, Australia
| | - Moira Blyth
- Yorkshire Regional Genetics Service, The Leeds Teaching Hospitals NHS Trust, Chapel Allerton Hospital, Leeds, UK
| | - Lydia Green
- Paediatric Neurology, The Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK
| | - Gayatri Vadlamani
- Paediatric Neurology, The Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK
| | - Daniel Warren
- The Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK
| | - Ian Craven
- The Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK
| | - Miriam Fanjul-Fernandez
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | | | - Paul J Lockhart
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | - Adeline Vanderver
- Division of Neurology, Children's Hospital of Philadelphia and Perlman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Cas Simons
- Murdoch Children's Research Institute, Melbourne, Australia.,Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia
| | - Susan Gibb
- Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Royal Children's Hospital, Melbourne, Australia
| | - Simon Sadedin
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | | | - Susan M White
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Victorian Clinical Genetics Services, Melbourne, Australia
| | - John Christodoulou
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Victorian Clinical Genetics Services, Melbourne, Australia
| | - Olga Skibina
- Eastern Health Neurosciences, Box Hill Hospital, Monash University, Melbourne, Australia
| | - Jonathan Ruddle
- Royal Children's Hospital, Melbourne, Australia.,Centre for Eye Research Australia Ltd, East Melbourne, Victoria, Australia.,Department of Ophthalmology, University of Melbourne, Melbourne, Australia
| | - Tiong Y Tan
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Victorian Clinical Genetics Services, Melbourne, Australia
| | - Richard J Leventer
- Murdoch Children's Research Institute, Melbourne, Australia.,Department of Paediatrics, University of Melbourne, Melbourne, Australia.,Royal Children's Hospital, Melbourne, Australia
| | - John H Livingston
- Paediatric Neurology, The Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Leeds, UK
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
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23
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Bissig C, Croisé P, Heiligenstein X, Hurbain I, Lenk GM, Kaufman E, Sannerud R, Annaert W, Meisler MH, Weisman LS, Raposo G, van Niel G. The PIKfyve complex regulates the early melanosome homeostasis required for physiological amyloid formation. J Cell Sci 2019; 132:jcs.229500. [PMID: 30709920 DOI: 10.1242/jcs.229500] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 01/14/2019] [Indexed: 12/23/2022] Open
Abstract
The metabolism of PI(3,5)P2 is regulated by the PIKfyve, VAC14 and FIG4 complex, mutations in which are associated with hypopigmentation in mice. These pigmentation defects indicate a key, but as yet unexplored, physiological relevance of this complex in the biogenesis of melanosomes. Here, we show that PIKfyve activity regulates formation of amyloid matrix composed of PMEL protein within the early endosomes in melanocytes, called stage I melanosomes. PIKfyve activity controls the membrane remodeling of stage I melanosomes, which regulates PMEL abundance, sorting and processing. PIKfyve activity also affects stage I melanosome kiss-and-run interactions with lysosomes, which are required for PMEL amyloidogenesis and the establishment of melanosome identity. Mechanistically, PIKfyve activity promotes both the formation of membrane tubules from stage I melanosomes and their release by modulating endosomal actin branching. Taken together, our data indicate that PIKfyve activity is a key regulator of the melanosomal import-export machinery that fine tunes the formation of functional amyloid fibrils in melanosomes and the maintenance of melanosome identity.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Christin Bissig
- Structure and Membrane Compartments, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France
| | - Pauline Croisé
- IPNP, Institute of Psychiatry and Neuroscience of Paris, Hopital Saint-Anne, Université Paris Descartes, INSERM U894, 75014 Paris, France
| | - Xavier Heiligenstein
- Structure and Membrane Compartments, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France.,Cell and Tissue Imaging Facility, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France
| | - Ilse Hurbain
- Structure and Membrane Compartments, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France.,Cell and Tissue Imaging Facility, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Emily Kaufman
- Life Science Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
| | - Ragna Sannerud
- VIB Center for Brain & Disease Research, 3000 Leuven, Belgium.,KU Leuven, Department of Neurosciences, 3000 Leuven, Belgium
| | - Wim Annaert
- VIB Center for Brain & Disease Research, 3000 Leuven, Belgium.,KU Leuven, Department of Neurosciences, 3000 Leuven, Belgium
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Lois S Weisman
- Life Science Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
| | - Graça Raposo
- Structure and Membrane Compartments, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France.,Cell and Tissue Imaging Facility, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France
| | - Guillaume van Niel
- Structure and Membrane Compartments, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France .,IPNP, Institute of Psychiatry and Neuroscience of Paris, Hopital Saint-Anne, Université Paris Descartes, INSERM U894, 75014 Paris, France.,Cell and Tissue Imaging Facility, Institut Curie, Paris Sciences & Lettres Research University, Centre National de la Recherche Scientifique, UMR144, 75005 Paris, France
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24
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Chen C, Holth JK, Bunton-Stasyshyn R, Anumonwo CK, Meisler MH, Noebels JL, Isom LL. Mapt deletion fails to rescue premature lethality in two models of sodium channel epilepsy. Ann Clin Transl Neurol 2018; 5:982-987. [PMID: 30128323 PMCID: PMC6093838 DOI: 10.1002/acn3.599] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 06/04/2018] [Indexed: 12/18/2022] Open
Abstract
Deletion of Mapt, encoding the microtubule‐binding protein Tau, prevents disease in multiple genetic models of hyperexcitability. To investigate whether the effect of Tau depletion is generalizable across multiple sodium channel gene‐linked models of epilepsy, we examined the Scn1b−/− mouse model of Dravet syndrome, and the Scn8aN1768D/+ model of Early Infantile Epileptic Encephalopathy. Both models display severe seizures and early mortality. We found no prolongation of survival between Scn1b−/−,Mapt+/+, Scn1b−/−,Mapt+/−, or Scn1b−/−,Mapt−/− mice or between Scn8aN1768D/+,Mapt+/+, Scn8aN1768D/+,Mapt+/−, or Scn8aN1768D/+,Mapt−/− mice. Thus, the effect of Mapt deletion on mortality in epileptic encephalopathy models is gene specific and provides further mechanistic insight.
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Affiliation(s)
- Chunling Chen
- Department of Pharmacology University of Michigan Medical School Ann Arbor Michigan 48109
| | - Jerrah K Holth
- Department of Neurology Baylor College of Medicine Houston Texas 77030.,Department of Molecular and Human Genetics Baylor College of Medicine Houston Texas 77030.,Present address: Department of Neurology Washington University St. Louis Missouri 63110
| | - Rosie Bunton-Stasyshyn
- Department of Human Genetics University of Michigan Medical School Ann Arbor Michigan 48109
| | - Charles K Anumonwo
- Department of Pharmacology University of Michigan Medical School Ann Arbor Michigan 48109
| | - Miriam H Meisler
- Department of Human Genetics University of Michigan Medical School Ann Arbor Michigan 48109
| | - Jeffrey L Noebels
- Department of Neurology Baylor College of Medicine Houston Texas 77030.,Department of Molecular and Human Genetics Baylor College of Medicine Houston Texas 77030
| | - Lori L Isom
- Department of Pharmacology University of Michigan Medical School Ann Arbor Michigan 48109
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25
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Baker EM, Thompson CH, Hawkins NA, Wagnon JL, Wengert ER, Patel MK, George AL, Meisler MH, Kearney JA. The novel sodium channel modulator GS-458967 (GS967) is an effective treatment in a mouse model of SCN8A encephalopathy. Epilepsia 2018; 59:1166-1176. [PMID: 29782051 DOI: 10.1111/epi.14196] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2018] [Indexed: 01/17/2023]
Abstract
OBJECTIVE De novo mutations of SCN8A, encoding the voltage-gated sodium channel NaV 1.6, have been associated with a severe infant onset epileptic encephalopathy. Individuals with SCN8A encephalopathy have a mean age of seizure onset of 4-5 months, with multiple seizure types that are often refractory to treatment with available drugs. Anecdotal reports suggest that high-dose phenytoin is effective for some patients, but there are associated adverse effects and potential for toxicity. Functional characterization of several SCN8A encephalopathy variants has shown that elevated persistent sodium current is one of several common biophysical defects. Therefore, specifically targeting elevated persistent current may be a useful therapeutic strategy in some cases. METHODS The novel sodium channel modulator GS967 has greater preference for persistent as opposed to peak current and nearly 10-fold greater potency than phenytoin. We evaluated the therapeutic effect of GS967 in the Scn8aN1768D/+ mouse model carrying an SCN8A patient mutation that results in elevated persistent sodium current. We also performed patch clamp recordings to assess the effect of GS967 on peak and persistent sodium current and excitability in hippocampal neurons from Scn8aN1768D/+ mice. RESULTS GS967 potently blocked persistent sodium current without affecting peak current, normalized action potential morphology, and attenuated excitability in neurons from heterozygous Scn8aN1768D/+ mice. Acute treatment with GS967 provided dose-dependent protection against maximal electroshock-induced seizures in Scn8aN1768D/+ and wild-type mice. Chronic treatment of Scn8aN1768D/+ mice with GS967 resulted in lower seizure burden and complete protection from seizure-associated lethality observed in untreated Scn8aN1768D/+ mice. Protection was achieved at a chronic dose that did not cause overt behavioral toxicity or sedation. SIGNIFICANCE Persistent sodium current modulators like GS967 may be an effective precision targeting strategy for SCN8A encephalopathy and other functionally similar channelopathies when elevated persistent sodium current is the primary dysfunction.
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Affiliation(s)
- Erin M Baker
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Christopher H Thompson
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Nicole A Hawkins
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Eric R Wengert
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Jennifer A Kearney
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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26
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Wagnon JL, Mencacci NE, Barker BS, Wengert ER, Bhatia KP, Balint B, Carecchio M, Wood NW, Patel MK, Meisler MH. Partial loss-of-function of sodium channel SCN8A in familial isolated myoclonus. Hum Mutat 2018; 39:965-969. [PMID: 29726066 PMCID: PMC6032947 DOI: 10.1002/humu.23547] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 04/27/2018] [Accepted: 05/01/2018] [Indexed: 02/01/2023]
Abstract
Variants in the neuronal sodium channel gene SCN8A have been implicated in several neurological disorders. Early infantile epileptic encephalopathy type 13 results from de novo gain‐of‐function mutations that alter the biophysical properties of the channel. Complete loss‐of‐function variants of SCN8A have been identified in cases of isolated intellectual disability. We now report a novel heterozygous SCN8A variant, p.Pro1719Arg, in a small pedigree with five family members affected with autosomal dominant upper limb isolated myoclonus without seizures or cognitive impairment. Functional analysis of the p.Pro1719Arg variant in transfected neuron‐derived cells demonstrated greatly reduced Nav1.6 channel activity without altered gating properties. Hypomorphic alleles of Scn8a in the mouse are known to result in similar movement disorders. This study expands the phenotypic and functional spectrum of SCN8A variants to include inherited nonepileptic isolated myoclonus. SCN8A can be considered as a candidate gene for isolated movement disorders without seizures.
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Affiliation(s)
- Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
| | - Niccolò E Mencacci
- Department of Neurology, Northwestern University, Chicago, Illinois.,Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Bryan S Barker
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Eric R Wengert
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Kailash P Bhatia
- Sobell Department, Institute of Neurology, University College of London, London, UK
| | - Bettina Balint
- Sobell Department, Institute of Neurology, University College of London, London, UK
| | - Miryam Carecchio
- Molecular Neurogenetics Unit, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy.,Department of Pediatric Neurology, IRCCS Foundation Carlo Besta Neurological Institute, Milan, Italy.,Department of Medicine and Surgery, PhD Programme in Molecular and Translational Medicine, Milan Bicocca University, Monza, Italy
| | - Nicholas W Wood
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia, Charlottesville, Virginia.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan.,Department of Neurology, University of Michigan, Ann Arbor, Michigan
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27
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Malcolmson J, Kleyner R, Tegay D, Adams W, Ward K, Coppinger J, Nelson L, Meisler MH, Wang K, Robison R, Lyon GJ. SCN8A mutation in a child presenting with seizures and developmental delays. Cold Spring Harb Mol Case Stud 2017; 2:a001073. [PMID: 27900360 PMCID: PMC5111007 DOI: 10.1101/mcs.a001073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The SCN8A gene encodes the sodium voltage-gated channel alpha subunit 8. Mutations in this gene have been associated with early infantile epileptic encephalopathy type 13. With the use of whole-exome sequencing, a de novo missense mutation in SCN8A was identified in a 4-yr-old female who initially exhibited symptoms of epilepsy at the age of 5 mo that progressed to a severe condition with very little movement, including being unable to sit or walk on her own.
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Affiliation(s)
- Janet Malcolmson
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA;; Genetic Counseling Graduate Program, Long Island University (LIU), Brookville, New York 11548, USA
| | - Robert Kleyner
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - David Tegay
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Whit Adams
- Utah Foundation for Biomedical Research, Salt Lake City, Utah 84107, USA
| | - Kenneth Ward
- Affiliated Genetics, Salt Lake City, Utah 84109, USA
| | | | - Lesa Nelson
- Affiliated Genetics, Salt Lake City, Utah 84109, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan 48109-5618, USA
| | - Kai Wang
- Utah Foundation for Biomedical Research, Salt Lake City, Utah 84107, USA;; Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90089, USA;; Department of Psychiatry and Behavioral Sciences, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
| | - Reid Robison
- Utah Foundation for Biomedical Research, Salt Lake City, Utah 84107, USA
| | - Gholson J Lyon
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA;; Utah Foundation for Biomedical Research, Salt Lake City, Utah 84107, USA
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28
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Stutterd C, Diakumis P, Bahlo M, Fanjul Fernandez M, Leventer RJ, Delatycki M, Amor D, Chow CW, Stephenson S, Meisler MH, Mclean C, Lockhart PJ. Neuropathology of childhood-onset basal ganglia degeneration caused by mutation of VAC14. Ann Clin Transl Neurol 2017; 4:859-864. [PMID: 29296614 PMCID: PMC5740235 DOI: 10.1002/acn3.487] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 09/08/2017] [Indexed: 11/08/2022] Open
Abstract
Objective To characterize the clinical features and neuropathology associated with recessive VAC14 mutations. Methods Whole-exome sequencing was used to identify the genetic etiology of a rapidly progressive neurological disease presenting in early childhood in two deceased siblings with distinct neuropathological features on post mortem examination. Results We identified compound heterozygous variants in VAC14 in two deceased siblings with early childhood onset of severe, progressive dystonia, and neurodegeneration. Their clinical phenotype is consistent with the VAC14-related childhood-onset, striatonigral degeneration recently described in two unrelated children. Post mortem examination demonstrated prominent vacuolation associated with degenerating neurons in the caudate nucleus, putamen, and globus pallidus, similar to previously reported ex vivo vacuoles seen in the late-endosome/lysosome of VAC14-deficient neurons. We identified upregulation of ubiquitinated granules within the cell cytoplasm and lysosomal-associated membrane protein (LAMP2) around the vacuole edge to suggest a process of vacuolation of lysosomal structures associated with active autophagocytic-associated neuronal degeneration. Interpretation Our findings reveal a distinct clinicopathological phenotype associated with recessive VAC14 mutations.
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Affiliation(s)
- Chloe Stutterd
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Victorian Clinical Genetics Service Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Neurology Royal Children's Hospital Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
| | - Peter Diakumis
- Walter and Eliza Hall Institute Parkville Victoria 3052 Australia
| | - Melanie Bahlo
- Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia.,Walter and Eliza Hall Institute Parkville Victoria 3052 Australia
| | - Miriam Fanjul Fernandez
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Victorian Clinical Genetics Service Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
| | - Richard J Leventer
- Department of Neurology Royal Children's Hospital Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia.,Neuroscience Research Group Murdoch Childrens Research Institute Parkville Victoria 3052 Australia
| | - Martin Delatycki
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Victorian Clinical Genetics Service Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
| | - David Amor
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Victorian Clinical Genetics Service Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Neurology Royal Children's Hospital Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
| | - Chung W Chow
- Department of Pathology Royal Children's Hospital Parkville Victoria 3052 Australia
| | - Sarah Stephenson
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
| | - Miriam H Meisler
- Department of Human Genetics University of Michigan School of Medicine Ann Arbor Michigan.,Department of Neurology University of Michigan School of Medicine Ann Arbor Michigan
| | - Catriona Mclean
- Anatomical Pathology Alfred Hospital Melbourne Victoria 3004 Australia
| | - Paul J Lockhart
- Bruce Lefroy Centre for Genetic Health Research Murdoch Childrens Research Institute Parkville Victoria 3052 Australia.,Department of Paediatrics The University of Melbourne Parkville Victoria 3052 Australia
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29
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Rolvien T, Butscheidt S, Jeschke A, Neu A, Denecke J, Kubisch C, Meisler MH, Pueschel K, Barvencik F, Yorgan T, Oheim R, Schinke T, Amling M. Severe bone loss and multiple fractures in SCN8A-related epileptic encephalopathy. Bone 2017; 103:136-143. [PMID: 28676440 DOI: 10.1016/j.bone.2017.06.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 06/20/2017] [Accepted: 06/30/2017] [Indexed: 10/19/2022]
Abstract
Mutations in the SCN8A gene encoding the neuronal voltage-gated sodium channel Nav1.6 are known to be associated with epileptic encephalopathy type 13. We identified a novel de novo SCN8A mutation (p.Phe360Ala, c.1078_1079delTTinsGC, Exon 9) in a 6-year-old girl with epileptic encephalopathy accompanied by severe juvenile osteoporosis and multiple skeletal fractures, similar to three previous case reports. Skeletal assessment using dual energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT) and serum analyses revealed a combined trabecular and cortical bone loss syndrome with elevated bone resorption. Likewise, when we analyzed the skeletal phenotype of 2week-old Scn8a-deficient mice we observed reduced trabecular and cortical bone mass, as well as increased osteoclast indices by histomorphometric quantification. Based on this cumulative evidence the patient was treated with neridronate (2mg/kg body weight administered every 3months), which fully prevented additional skeletal fractures for the next 25months. Taken together, our data provide evidence for a negative impact of SCN8A mutations on bone mass, which can be positively influenced by anti-resorptive treatment.
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Affiliation(s)
- Tim Rolvien
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany; Department of Orthopaedic Surgery, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany
| | - Sebastian Butscheidt
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Anke Jeschke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Axel Neu
- Department of Neuropediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jonas Denecke
- Department of Neuropediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christian Kubisch
- Department of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Klaus Pueschel
- Department of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Florian Barvencik
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Timur Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Ralf Oheim
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 59, 22529 Hamburg, Germany.
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Wagnon JL, Barker BS, Ottolini M, Park Y, Volkheimer A, Valdez P, Swinkels MEM, Patel MK, Meisler MH. Loss-of-function variants of SCN8A in intellectual disability without seizures. Neurol Genet 2017; 3:e170. [PMID: 28702509 PMCID: PMC5499976 DOI: 10.1212/nxg.0000000000000170] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/11/2017] [Indexed: 11/15/2022]
Abstract
Objective: To determine the functional effect of SCN8A missense mutations in 2 children with intellectual disability and developmental delay but no seizures. Methods: Genomic DNA was analyzed by next-generation sequencing. SCN8A variants were introduced into the Nav1.6 complementary DNA by site-directed mutagenesis. Channel activity was measured electrophysiologically in transfected ND7/23 cells. The stability of the mutant channels was assessed by Western blot. Results: Both children were heterozygous for novel missense variants that altered conserved residues in transmembrane segments of Nav1.6, p.Gly964Arg in D2S6 and p.Glu1218Lys in D3S1. Both altered amino acids are evolutionarily conserved in vertebrate and invertebrate channels and are predicted to be deleterious. Neither was observed in the general population. Both variants completely prevented the generation of sodium currents in transfected cells. The abundance of Nav1.6 protein was reduced by the Glu1218Lys substitution. Conclusions: Haploinsufficiency of SCN8A is associated with cognitive impairment. These observations extend the phenotypic spectrum of SCN8A mutations beyond their established role in epileptic encephalopathy (OMIM#614558) and other seizure disorders. SCN8A should be considered as a candidate gene for intellectual disability, regardless of seizure status.
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Affiliation(s)
- Jacy L Wagnon
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Bryan S Barker
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Matteo Ottolini
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Young Park
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Alicia Volkheimer
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Purnima Valdez
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Marielle E M Swinkels
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Manoj K Patel
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
| | - Miriam H Meisler
- Department of Human Genetics (J.L.W., Y.P., M.H.M.), University of Michigan, Ann Arbor; Department of Anesthesiology (B.S.B., M.O., M.K.P.) and Neuroscience Graduate Program (B.S.B., M.K.P.), University of Virginia, Charlottesville; Department of Medicine (A.V.), Veterans Affairs Medical Center (A.V.), and Department of Pediatrics (P.V.), Duke University, Durham, NC; and Department of Medical Genetics (M.E.M.S.), University Medical Centre Utrecht, the Netherlands
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Sprissler RS, Wagnon JL, Bunton-Stasyshyn RK, Meisler MH, Hammer MF. Altered gene expression profile in a mouse model of SCN8A encephalopathy. Exp Neurol 2016; 288:134-141. [PMID: 27836728 DOI: 10.1016/j.expneurol.2016.11.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/06/2016] [Accepted: 11/03/2016] [Indexed: 02/07/2023]
Abstract
SCN8A encephalopathy is a severe, early-onset epilepsy disorder resulting from de novo gain-of-function mutations in the voltage-gated sodium channel Nav1.6. To identify the effects of this disorder on mRNA expression, RNA-seq was performed on brain tissue from a knock-in mouse expressing the patient mutation p.Asn1768Asp (N1768D). RNA was isolated from forebrain, cerebellum, and brainstem both before and after seizure onset, and from age-matched wildtype littermates. Altered transcript profiles were observed only in forebrain and only after seizures. The abundance of 50 transcripts increased more than 3-fold and 15 transcripts decreased more than 3-fold after seizures. The elevated transcripts included two anti-convulsant neuropeptides and more than a dozen genes involved in reactive astrocytosis and response to neuronal damage. There was no change in the level of transcripts encoding other voltage-gated sodium, potassium or calcium channels. Reactive astrocytosis was observed in the hippocampus of mutant mice after seizures. There is considerable overlap between the genes affected in this genetic model of epilepsy and those altered by chemically induced seizures, traumatic brain injury, ischemia, and inflammation. The data support the view that gain-of-function mutations of SCN8A lead to pathogenic alterations in brain function contributing to encephalopathy.
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Affiliation(s)
- Ryan S Sprissler
- ARL Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | | | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Michael F Hammer
- ARL Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA; Department of Neurology, University of Arizona, Tucson, AZ 85721, USA.
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Lenk GM, Szymanska K, Debska-Vielhaber G, Rydzanicz M, Walczak A, Bekiesinska-Figatowska M, Vielhaber S, Hallmann K, Stawinski P, Buehring S, Hsu DA, Kunz WS, Meisler MH, Ploski R. Biallelic Mutations of VAC14 in Pediatric-Onset Neurological Disease. Am J Hum Genet 2016; 99:188-94. [PMID: 27292112 DOI: 10.1016/j.ajhg.2016.05.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 05/02/2016] [Indexed: 01/29/2023] Open
Abstract
In the PI(3,5)P2 biosynthetic complex, the lipid kinase PIKFYVE and the phosphatase FIG4 are bound to the dimeric scaffold protein VAC14, which is composed of multiple heat-repeat domains. Mutations of FIG4 result in the inherited disorders Charcot-Marie-Tooth disease type 4J, Yunis-Varón syndrome, and polymicrogyria with seizures. We here describe inherited variants of VAC14 in two unrelated children with sudden onset of a progressive neurological disorder and regression of developmental milestones. Both children developed impaired movement with dystonia, became nonambulatory and nonverbal, and exhibited striatal abnormalities on MRI. A diagnosis of Leigh syndrome was rejected due to normal lactate profiles. Exome sequencing identified biallelic variants of VAC14 that were inherited from unaffected heterozygous parents in both families. Proband 1 inherited a splice-site variant that results in skipping of exon 13, p.Ile459Profs(∗)4 (not reported in public databases), and the missense variant p.Trp424Leu (reported in the ExAC database in a single heterozygote). Proband 2 inherited two missense variants in the dimerization domain of VAC14, p.Ala582Ser and p.Ser583Leu, that have not been previously reported. Cultured skin fibroblasts exhibited the accumulation of vacuoles that is characteristic of PI(3,5)P2 deficiency. Vacuolization of fibroblasts was rescued by transfection of wild-type VAC14 cDNA. The similar age of onset and neurological decline in the two unrelated children define a recessive disorder resulting from compound heterozygosity for deleterious variants of VAC14.
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Affiliation(s)
- Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Krystyna Szymanska
- Department of Child Psychiatry, Warsaw Medical University, 02-106 Warsaw, Poland; Department of Experimental and Clinical Neuropathology, Medical Research Center, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | | | - Malgorzata Rydzanicz
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland
| | - Anna Walczak
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland
| | | | - Stefan Vielhaber
- Klinik für Neurologie, Universitätsklinikum Magdeburg, 39120 Magdeburg, Germany
| | - Kerstin Hallmann
- Klinik für Epileptologie and Life&Brain Center, Universitätsklinikum Bonn, 53105 Bonn, Germany
| | - Piotr Stawinski
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland; Institute of Physiology and Pathology of Hearing, 05-830 Nadarzyn, Poland
| | | | - David A Hsu
- Department of Neurology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Wolfram S Kunz
- Klinik für Epileptologie and Life&Brain Center, Universitätsklinikum Bonn, 53105 Bonn, Germany
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
| | - Rafal Ploski
- Department of Medical Genetics, Warsaw Medical University, 02-106 Warsaw, Poland.
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33
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Barker BS, Ottolini M, Wagnon JL, Hollander RM, Meisler MH, Patel MK. The SCN8A encephalopathy mutation p.Ile1327Val displays elevated sensitivity to the anticonvulsant phenytoin. Epilepsia 2016; 57:1458-66. [PMID: 27375106 DOI: 10.1111/epi.13461] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2016] [Indexed: 12/16/2022]
Abstract
OBJECTIVE SCN8A encephalopathy (early infantile epileptic encephalopathy; EIEE13) is caused by gain-of-function mutations resulting in hyperactivity of the voltage-gated sodium channel Nav 1.6. The channel is concentrated at the axon initial segment (AIS) and is involved in establishing neuronal excitability. Clinical features of SCN8A encephalopathy include seizure onset between 0 and 18 months of age, intellectual disability, and developmental delay. Seizures are often refractory to treatment with standard antiepileptic drugs, and sudden unexpected death in epilepsy (SUDEP) has been reported in approximately 10% of patients. In a recent study, high doses of phenytoin were effective in four patients with SCN8A encephalopathy. In view of this observation, we have investigated the relationship between the functional effect of the SCN8A mutation p.Ile1327Val and its response to phenytoin. METHODS The mutation was introduced into the Scn8a cDNA by site-directed mutagenesis. Channel activity was characterized in transfected ND7/23 cells. The effects of phenytoin (100 μm) on mutant and wild-type (WT) channels were compared. RESULTS Channel activation parameters were shifted in a hyperpolarizing direction in the mutant channel, whereas inactivation parameters were shifted in a depolarizing direction, increasing Na channel window current. Macroscopic current decay was slowed in I1327V channels, indicating an impairment in the transition from open state to inactivated state. Channel deactivation was also delayed, allowing more channels to remain in the open state. Phenytoin (100 μm) resulted in hyperpolarized activation and inactivation curves as well as greater tonic block and use-dependent block of I1327V mutant channels relative to WT. SIGNIFICANCE SCN8A - I1327V is a gain-of-function mutation with altered features that are predicted to increase neuronal excitability and seizure susceptibility. Phenytoin is an effective inhibitor of the mutant channel and may be of use in treating patients with gain-of-function mutations of SCN8A.
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Affiliation(s)
- Bryan S Barker
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, U.S.A.,Neuroscience Graduate Program, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Matteo Ottolini
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, U.S.A
| | - Rachel M Hollander
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, U.S.A
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, U.S.A
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, U.S.A.,Neuroscience Graduate Program, University of Virginia Health System, Charlottesville, Virginia, U.S.A
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Meisler MH, Helman G, Hammer MF, Fureman BE, Gaillard WD, Goldin AL, Hirose S, Ishii A, Kroner BL, Lossin C, Mefford HC, Parent JM, Patel M, Schreiber J, Stewart R, Whittemore V, Wilcox K, Wagnon JL, Pearl PL, Vanderver A, Scheffer IE. SCN8A encephalopathy: Research progress and prospects. Epilepsia 2016; 57:1027-35. [PMID: 27270488 PMCID: PMC5495462 DOI: 10.1111/epi.13422] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2016] [Indexed: 01/15/2023]
Abstract
On April 21, 2015, the first SCN8A Encephalopathy Research Group convened in Washington, DC, to assess current research into clinical and pathogenic features of the disorder and prepare an agenda for future research collaborations. The group comprised clinical and basic scientists and representatives of patient advocacy groups. SCN8A encephalopathy is a rare disorder caused by de novo missense mutations of the sodium channel gene SCN8A, which encodes the neuronal sodium channel Nav 1.6. Since the initial description in 2012, approximately 140 affected individuals have been reported in publications or by SCN8A family groups. As a result, an understanding of the severe impact of SCN8A mutations is beginning to emerge. Defining a genetic epilepsy syndrome goes beyond identification of molecular etiology. Topics discussed at this meeting included (1) comparison between mutations of SCN8A and the SCN1A mutations in Dravet syndrome, (2) biophysical properties of the Nav 1.6 channel, (3) electrophysiologic effects of patient mutations on channel properties, (4) cell and animal models of SCN8A encephalopathy, (5) drug screening strategies, (6) the phenotypic spectrum of SCN8A encephalopathy, and (7) efforts to develop a bioregistry. A panel discussion of gaps in bioregistry, biobanking, and clinical outcomes data was followed by a planning session for improved integration of clinical and basic science research. Although SCN8A encephalopathy was identified only recently, there has been rapid progress in functional analysis and phenotypic classification. The focus is now shifting from identification of the underlying molecular cause to the development of strategies for drug screening and prioritized patient care.
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Affiliation(s)
- Miriam H. Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, U.S.A
| | - Guy Helman
- Department of Neurology, Children’s National Health System, Washington, District of Columbia, U.S.A
- Center for Genetic Medicine Research, Children’s National Health System, Washington, District of Columbia, U.S.A
| | - Michael F. Hammer
- ARL Division of Biotechnology, University of Arizona, Tucson, Arizona, U.S.A
| | - Brandy E. Fureman
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - William D. Gaillard
- Department of Neurology, Children’s National Health System, Washington, District of Columbia, U.S.A
- Center for Neuroscience Research, Children’s National Health System, Washington, District of Columbia, U.S.A
| | - Alan L. Goldin
- Microbiology & Molecular Genetics and Anatomy & Neurobiology, University of California, Irvine, California, U.S.A
| | - Shinichi Hirose
- Department of Pediatrics, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Atsushi Ishii
- Department of Pediatrics, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Barbara L. Kroner
- Biostatistics and Epidemiology, RTI International, Rockville, Maryland, U.S.A
| | - Christoph Lossin
- Department of Neurology, School of Medicine, University of California Davis, Sacramento, California, U.S.A
| | - Heather C. Mefford
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, Washington, U.S.A
| | - Jack M. Parent
- Department of Neurology, University of Michigan Medical Center and VA Ann Arbor Healthcare System, Ann Arbor, Michigan, U.S.A
| | - Manoj Patel
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, U.S.A
| | - John Schreiber
- Department of Neurology, Children’s National Health System, Washington, District of Columbia, U.S.A
| | - Randall Stewart
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Vicky Whittemore
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Karen Wilcox
- Anticonvulsant Drug Development Program, Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah, U.S.A
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, U.S.A
| | - Phillip L. Pearl
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - Adeline Vanderver
- Department of Neurology, Children’s National Health System, Washington, District of Columbia, U.S.A
- Center for Genetic Medicine Research, Children’s National Health System, Washington, District of Columbia, U.S.A
- Department of Integrated Systems Biology and Pediatrics, George Washington University, Washington, District of Columbia, U.S.A
| | - Ingrid E. Scheffer
- Department of Neurology, Royal Children’s Hospital, Melbourne, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
- Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Melbourne, Victoria, Australia
- Florey Institute of Neurosciences and Mental Health, Melbourne, Victoria, Australia
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35
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He F, Jones JM, Figueroa-Romero C, Zhang D, Feldman EL, Goutman SA, Meisler MH, Callaghan BC, Todd PK. Screening for novel hexanucleotide repeat expansions at ALS- and FTD-associated loci. Neurol Genet 2016; 2:e71. [PMID: 27274540 PMCID: PMC4865132 DOI: 10.1212/nxg.0000000000000071] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 03/01/2016] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To determine whether GGGGCC (G4C2) repeat expansions at loci other than C9orf72 serve as common causes of amyotrophic lateral sclerosis (ALS). METHODS We assessed G4C2 repeat number in 28 genes near known ALS and frontotemporal dementia (FTD) loci by repeat-primed PCR coupled with fluorescent fragment analysis in 199 patients with ALS (17 familial, 182 sporadic) and 136 healthy controls. We also obtained blood from patients with ALS4 for evaluation of repeats surrounding the SETX gene locus. C9orf72 expansions were evaluated in parallel. RESULTS Expansions of G4C2 repeats in C9orf72 explained 8.8% of sporadic and 47% of familial ALS cases analyzed. Repeat variance was observed at one other locus, RGS14, but no large expansions were observed, and repeat sizes were not different between cases and controls. No G4C2 repeat expansions were identified at other ALS or FTD risk loci or in ALS4 cases. CONCLUSIONS G4C2 expansions near known ALS and FTD loci other than C9orf72 are not a common cause of ALS.
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Affiliation(s)
- Fang He
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Julie M Jones
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Claudia Figueroa-Romero
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Dapeng Zhang
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Eva L Feldman
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Stephen A Goutman
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Miriam H Meisler
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Brian C Callaghan
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
| | - Peter K Todd
- Department of Neurology (F.H., C.F.-R., B.C.C., E.L.F., S.A.G., P.K.T.) and Department of Human Genetics (J.M.J., M.H.M.), University of Michigan, Ann Arbor; Veteran Association Health System (B.C.C., P.K.T.), Ann Arbor; and National Center for Biotechnology Information (D.Z.), National Institutes of Health, Bethesda, MD
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Jones JM, Dionne L, Dell'Orco J, Parent R, Krueger JN, Cheng X, Dib-Hajj SD, Bunton-Stasyshyn RK, Sharkey LM, Dowling JJ, Murphy GG, Shakkottai VG, Shrager P, Meisler MH. Single amino acid deletion in transmembrane segment D4S6 of sodium channel Scn8a (Nav1.6) in a mouse mutant with a chronic movement disorder. Neurobiol Dis 2016; 89:36-45. [PMID: 26807988 PMCID: PMC4991781 DOI: 10.1016/j.nbd.2016.01.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 01/06/2016] [Accepted: 01/20/2016] [Indexed: 02/08/2023] Open
Abstract
Mutations of the neuronal sodium channel gene SCN8A are associated with lethal movement disorders in the mouse and with human epileptic encephalopathy. We describe a spontaneous mouse mutation, Scn8a(9J), that is associated with a chronic movement disorder with early onset tremor and adult onset dystonia. Scn8a(9J) homozygotes have a shortened lifespan, with only 50% of mutants surviving beyond 6 months of age. The 3 bp in-frame deletion removes 1 of the 3 adjacent isoleucine residues in transmembrane segment DIVS6 of Nav1.6 (p.Ile1750del). The altered helical orientation of the transmembrane segment displaces pore-lining amino acids with important roles in channel activation and inactivation. The predicted impact on channel activity was confirmed by analysis of cerebellar Purkinje neurons from mutant mice, which lack spontaneous and induced repetitive firing. In a heterologous expression system, the activity of the mutant channel was below the threshold for detection. Observations of decreased nerve conduction velocity and impaired behavior in an open field are also consistent with reduced activity of Nav1.6. The Nav1.6Δ1750 protein is only partially glycosylated. The abundance of mutant Nav1.6 is reduced at nodes of Ranvier and is not detectable at the axon initial segment. Despite a severe reduction in channel activity, the lifespan and motor function of Scn8a(9J/9J) mice are significantly better than null mutants lacking channel protein. The clinical phenotype of this severe hypomorphic mutant expands the spectrum of Scn8a disease to include a recessively inherited, chronic and progressive movement disorder.
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Affiliation(s)
- Julie M Jones
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, United States
| | - Louise Dionne
- The Jackson Laboratory, Bar Harbor, ME 04609, United States
| | - James Dell'Orco
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Rachel Parent
- Department of Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Jamie N Krueger
- Department of Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Xiaoyang Cheng
- Department of Neurology and Centre for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06516, United States.
| | - Sulayman D Dib-Hajj
- Department of Neurology and Centre for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06516, United States
| | | | - Lisa M Sharkey
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, United States
| | - James J Dowling
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Geoffrey G Murphy
- Department of Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Peter Shrager
- Department of Neurobiology & Anatomy, University of Rochester Medical Center, Rochester, NY 14642, United States
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, United States.
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Mironova YA, Lenk GM, Lin JP, Lee SJ, Twiss JL, Vaccari I, Bolino A, Havton LA, Min SH, Abrams CS, Shrager P, Meisler MH, Giger RJ. PI(3,5)P2 biosynthesis regulates oligodendrocyte differentiation by intrinsic and extrinsic mechanisms. eLife 2016; 5. [PMID: 27008179 PMCID: PMC4889328 DOI: 10.7554/elife.13023] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/23/2016] [Indexed: 12/18/2022] Open
Abstract
Proper development of the CNS axon-glia unit requires bi-directional communication between axons and oligodendrocytes (OLs). We show that the signaling lipid phosphatidylinositol-3,5-bisphosphate [PI(3,5)P2] is required in neurons and in OLs for normal CNS myelination. In mice, mutations of Fig4, Pikfyve or Vac14, encoding key components of the PI(3,5)P2 biosynthetic complex, each lead to impaired OL maturation, severe CNS hypomyelination and delayed propagation of compound action potentials. Primary OLs deficient in Fig4 accumulate large LAMP1+ and Rab7+ vesicular structures and exhibit reduced membrane sheet expansion. PI(3,5)P2 deficiency leads to accumulation of myelin-associated glycoprotein (MAG) in LAMP1+perinuclear vesicles that fail to migrate to the nascent myelin sheet. Live-cell imaging of OLs after genetic or pharmacological inhibition of PI(3,5)P2 synthesis revealed impaired trafficking of plasma membrane-derived MAG through the endolysosomal system in primary cells and brain tissue. Collectively, our studies identify PI(3,5)P2 as a key regulator of myelin membrane trafficking and myelinogenesis. DOI:http://dx.doi.org/10.7554/eLife.13023.001 Neurons communicate with each other through long cable-like extensions called axons. An insulating sheath called myelin (or white matter) surrounds each axon, and allows electrical impulses to travel more quickly. Cells in the brain called oligodendrocytes produce myelin. If the myelin sheath is not properly formed during development, or is damaged by injury or disease, the consequences can include paralysis, impaired thought, and loss of vision. Oligodendrocytes have complex shapes, and each can generate myelin for as many as 50 axons. Oligodendrocytes produce the building blocks of myelin inside their cell bodies, by following instructions encoded by genes within the nucleus. However, the signals that regulate the trafficking of these components to the myelin sheath are poorly understood. Mironova et al. set out to determine whether signaling molecules called phosphoinositides help oligodendrocytes to mature and move myelin building blocks from the cell bodies to remote contact points with axons. Genetic techniques were used to manipulate an enzyme complex in mice that controls the production and turnover of a phosphoinositide called PI(3,5)P2. Mironova et al. found that reducing the levels of PI(3,5)P2 in oligodendrocytes caused the trafficking of certain myelin building blocks to stall. Key myelin components instead accumulated inside bubble-like structures near the oligodendrocyte’s cell body. This showed that PI(3,5)P2 in oligodendrocytes is essential for generating myelin. Further experiments then revealed that reducing PI(3,5)P2 in the neurons themselves indirectly prevented the oligodendrocytes from maturing. This suggests that PI(3,5)P2 also takes part in communication between axons and oligodendrocytes during development of the myelin sheath. A key next step will be to identify the regulatory mechanisms that control the production of PI(3,5)P2 in oligodendrocytes and neurons. Future studies could also explore what PI(3,5)P2 acts upon inside the axons, and which signaling molecules support the maturation of oligodendrocytes. Finally, it remains unclear whether PI(3,5)P2signaling is also required for stabilizing mature myelin, and for repairing myelin after injury in the adult brain. Further work could therefore address these questions as well. DOI:http://dx.doi.org/10.7554/eLife.13023.002
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Affiliation(s)
- Yevgeniya A Mironova
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, United States.,Cellular and Molecular Biology Graduate Program, University of Michigan School of Medicine, Ann Arbor, United States
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan School of Medicine, Ann Arbor, United States
| | - Jing-Ping Lin
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Seung Joon Lee
- Department of Biological Sciences, University of South Carolina, Columbia, United States
| | - Jeffery L Twiss
- Department of Biological Sciences, University of South Carolina, Columbia, United States
| | - Ilaria Vaccari
- Human Inherited Neuropathies Unit, INSPE-Institute for Experimental Neurology, San Raffaele Scientific Institute, Milan, Italy
| | - Alessandra Bolino
- Human Inherited Neuropathies Unit, INSPE-Institute for Experimental Neurology, San Raffaele Scientific Institute, Milan, Italy
| | - Leif A Havton
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Sang H Min
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, United States
| | - Charles S Abrams
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, United States
| | - Peter Shrager
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, United States
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan School of Medicine, Ann Arbor, United States.,Department of Neurology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Roman J Giger
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, United States.,Department of Neurology, University of Michigan School of Medicine, Ann Arbor, United States
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Wagnon JL, Barker BS, Hounshell JA, Haaxma CA, Shealy A, Moss T, Parikh S, Messer RD, Patel MK, Meisler MH. Pathogenic mechanism of recurrent mutations of SCN8A in epileptic encephalopathy. Ann Clin Transl Neurol 2015; 3:114-23. [PMID: 26900580 PMCID: PMC4748308 DOI: 10.1002/acn3.276] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 11/20/2015] [Indexed: 12/03/2022] Open
Abstract
Objective The early infantile epileptic encephalopathy type 13 (EIEE13, OMIM #614558) results from de novo missense mutations of SCN8A encoding the voltage‐gated sodium channel Nav1.6. More than 20% of patients have recurrent mutations in residues Arg1617 or Arg1872. Our goal was to determine the functional effects of these mutations on channel properties. Methods Clinical exome sequencing was carried out on patients with early‐onset seizures, developmental delay, and cognitive impairment. Two mutations identified here, p.Arg1872Leu and p.Arg1872Gln, and two previously identified mutations, p.Arg1872Trp and p.Arg1617Gln, were introduced into Nav1.6 cDNA, and effects on electrophysiological properties were characterized in transfected ND7/23 cells. Interactions with FGF14, G‐protein subunit Gβγ, and sodium channel subunit β1 were assessed by coimmunoprecipitation. Results We identified two patients with the novel mutation p.Arg1872Leu and one patient with the recurrent mutation p.Arg1872Gln. The three mutations of Arg1872 and the mutation of Arg1617 all impaired the sodium channel transition from open state to inactivated state, resulting in channel hyperactivity. Other observed abnormalities contributing to elevated channel activity were increased persistent current, increased peak current density, hyperpolarizing shift in voltage dependence of activation, and depolarizing shift in steady‐state inactivation. Protein interactions were not affected. Interpretation Recurrent mutations at Arg1617 and Arg1872 lead to elevated Nav1.6 channel activity by impairing channel inactivation. Channel hyperactivity is the major pathogenic mechanism for gain‐of‐function mutations of SCN8A. EIEE13 differs mechanistically from Dravet syndrome, which is caused by loss‐of‐function mutations of SCN1A. This distinction has important consequences for selection of antiepileptic drugs and the development of gene‐ and mutation‐specific treatments.
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Affiliation(s)
- Jacy L Wagnon
- Department of Human Genetics University of Michigan Ann Arbor Michigan
| | - Bryan S Barker
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - James A Hounshell
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - Charlotte A Haaxma
- Department of Pediatric Neurology Radboud University Nijmegen The Netherlands
| | - Amy Shealy
- Cleveland Clinic Genomic Medicine Institute Cleveland Ohio
| | - Timothy Moss
- Cleveland Clinic Genomic Medicine Institute Cleveland Ohio
| | - Sumit Parikh
- Department of Pediatric Neurology Cleveland Clinic Cleveland Ohio
| | - Ricka D Messer
- Department of Pediatric Neurology Johns Hopkins Medical Institute Baltimore Maryland
| | - Manoj K Patel
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - Miriam H Meisler
- Department of Human Genetics University of Michigan Ann Arbor Michigan
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Lenk GM, Frei CM, Miller AC, Wallen RC, Mironova YA, Giger RJ, Meisler MH. Rescue of neurodegeneration in the Fig4 null mouse by a catalytically inactive FIG4 transgene. Hum Mol Genet 2015; 25:340-7. [PMID: 26604144 DOI: 10.1093/hmg/ddv480] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/16/2015] [Indexed: 11/13/2022] Open
Abstract
The lipid phosphatase FIG4 is a subunit of the protein complex that regulates biosynthesis of the signaling lipid PI(3,5)P2. Mutations of FIG4 result in juvenile lethality and spongiform neurodegeneration in the mouse, and are responsible for the human disorders Charcot-Marie-Tooth disease, Yunis-Varon syndrome and polymicrogyria with seizures. We previously demonstrated that conditional expression of a wild-type FIG4 transgene in neurons is sufficient to rescue most of the abnormalities of Fig4 null mice, including juvenile lethality and extensive neurodegeneration. To evaluate the contribution of the phosphatase activity to the in vivo function of Fig4, we introduced the mutation p.Cys486Ser into the Sac phosphatase active-site motif CX5RT. Transfection of the Fig4(Cys486Ser) cDNA into cultured Fig4(-/-) fibroblasts was effective in preventing vacuolization. The neuronal expression of an NSE-Fig4(Cys486Ser) transgene in vivo prevented the neonatal neurodegeneration and juvenile lethality seen in Fig4 null mice. These observations demonstrate that the catalytically inactive FIG4 protein provides significant function, possibly by stabilization of the PI(3,5)P2 biosynthetic complex and/or localization of the complex to endolysosomal vesicles. Despite this partial rescue, later in life the NSE-Fig4(Cys486Ser) transgenic mice display significant abnormalities that include hydrocephalus, defective myelination and reduced lifespan. The late onset phenotype of the NSE-Fig4(Cys486Ser) transgenic mice demonstrates that the phosphatase activity of FIG4 has an essential role in vivo.
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Affiliation(s)
| | | | | | | | | | - Roman J Giger
- Department of Cell and Developmental Biology and Department of Neurology, University of Michigan, 4909 Buhl, Ann Arbor, MI 48109-5618, USA
| | - Miriam H Meisler
- Department of Human Genetics, Department of Neurology, University of Michigan, 4909 Buhl, Ann Arbor, MI 48109-5618, USA
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Abstract
OBJECTIVE De novo mutations of the gene sodium channel 1α (SCN1A) are the major cause of Dravet syndrome, an infantile epileptic encephalopathy. US incidence of DS has been estimated at 1 in 40 000, but no US epidemiologic studies have been performed since the advent of genetic testing. METHODS In a retrospective, population-based cohort of all infants born at Kaiser Permanente Northern California during 2007-2010, we electronically identified patients who received ≥2 seizure diagnoses before age 12 months and who were also prescribed anticonvulsants at 24 months. A child neurologist reviewed records to identify infants who met 4 of 5 criteria for clinical Dravet syndrome: normal development before seizure onset; ≥2 seizures before age 12 months; myoclonic, hemiclonic, or generalized tonic-clonic seizures; ≥2 seizures lasting >10 minutes; and refractory seizures after age 2 years. SCN1A gene sequencing was performed as part of routine clinical care. RESULTS Eight infants met the study criteria for clinical Dravet syndrome, yielding an incidence of 1 per 15 700. Six of these infants (incidence of 1 per 20 900) had a de novo SCN1A missense mutation that is likely to be pathogenic. One infant had an inherited SCN1A variant that is unlikely to be pathogenic. All 8 experienced febrile seizures, and 6 had prolonged seizures lasting >10 minutes by age 1 year. CONCLUSIONS Dravet syndrome due to an SCN1A mutation is twice as common in the United States as previously thought. Genetic testing should be considered in children with ≥2 prolonged febrile seizures by 1 year of age.
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Affiliation(s)
- Yvonne W. Wu
- Departments of Neurology and,Pediatrics, University of California, San Francisco, San Francisco, California
| | - Joseph Sullivan
- Departments of Neurology and,Pediatrics, University of California, San Francisco, San Francisco, California
| | | | - Miriam H. Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan
| | | | | | - Michael W. Kuzniewicz
- Research, and,Neonatology, Kaiser Permanente Northern California, Oakland, California; and
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Pal D, Jones JM, Wisidagamage S, Meisler MH, Mashour GA. Reduced Nav1.6 Sodium Channel Activity in Mice Increases In Vivo Sensitivity to Volatile Anesthetics. PLoS One 2015; 10:e0134960. [PMID: 26252017 PMCID: PMC4529172 DOI: 10.1371/journal.pone.0134960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 07/16/2015] [Indexed: 11/22/2022] Open
Abstract
Nav1.6 is a major voltage-gated sodium channel in the central and peripheral nervous systems. Within neurons, the channel protein is concentrated at the axon initial segment and nodes of Ranvier, where it functions in initiation and propagation of action potentials. We examined the role of Nav1.6 in general anesthesia using two mouse mutants with reduced activity of Nav1.6, Scn8amedJ/medJ and Scn8a9J/9J. The mice were exposed to the general anesthetics isoflurane and sevoflurane in step-wise increments; the concentration required to produce loss of righting reflex, a surrogate for anesthetic-induced unconsciousness in rodents, was determined. Mice homozygous for these mutations exhibited increased sensitivity to both isoflurane and sevoflurane. The increased sensitivity was observed during induction of unconsciousness but not during the recovery phase, suggesting that the effect is not attributable to compromised systemic physiology. Electroencephalographic theta power during baseline waking was lower in mutants, suggesting decreased arousal and reduced neuronal excitability. This is the first report linking reduced activity of a specific voltage-gated sodium channel to increased sensitivity to general anesthetics in vivo.
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Affiliation(s)
- Dinesh Pal
- Department of Anesthesiology, University of Michigan, 7433 Medical Science Building 1, 1150, West Medical Center Drive, Ann Arbor, Michigan, United States of America
- Center for Consciousness Science, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Julie M. Jones
- Department of Human Genetics, University of Michigan, 4808 Medical Science Building 2, 1241 East Catherine Street, Ann Arbor, Michigan, United States of America
| | - Stella Wisidagamage
- Department of Anesthesiology, University of Michigan, 7433 Medical Science Building 1, 1150, West Medical Center Drive, Ann Arbor, Michigan, United States of America
| | - Miriam H. Meisler
- Department of Human Genetics, University of Michigan, 4808 Medical Science Building 2, 1241 East Catherine Street, Ann Arbor, Michigan, United States of America
| | - George A. Mashour
- Department of Anesthesiology, University of Michigan, 7433 Medical Science Building 1, 1150, West Medical Center Drive, Ann Arbor, Michigan, United States of America
- Center for Consciousness Science, University of Michigan, Ann Arbor, Michigan, United States of America
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
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Abstract
Mutations of the voltage-gated sodium channel SCN8A have been identified in approximately 1% of nearly 1,500 children with early-infantile epileptic encephalopathies (EIEE) who have been tested by DNA sequencing. EIEE caused by mutation of SCN8A is designated EIEE13 (OMIM #614558). Affected children have seizure onset before 18 months of age as well as developmental and cognitive disabilities, movement disorders, and a high incidence of sudden death (SUDEP). EIEE13 is caused by de novo missense mutations of evolutionarily conserved residues in the Nav1.6 channel protein. One-third of the mutations are recurrent, and many occur at CpG dinucleotides. In this review, we discuss the effect of pathogenic mutations on the structure of the channel protein, the rate of recurrent mutation, and changes in channel function underlying this devastating disorder.
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Affiliation(s)
- Jacy L Wagnon
- Department of Human Genetics, University of Michigan , Ann Arbor, MI , USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan , Ann Arbor, MI , USA
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Menezes MP, Waddell L, Lenk GM, Kaur S, MacArthur DG, Meisler MH, Clarke NF. Response. Neuromuscul Disord 2015; 25:360. [DOI: 10.1016/j.nmd.2014.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Blanchard MG, Willemsen MH, Walker JB, Dib-Hajj SD, Waxman SG, Jongmans MCJ, Kleefstra T, van de Warrenburg BP, Praamstra P, Nicolai J, Yntema HG, Bindels RJM, Meisler MH, Kamsteeg EJ. De novo gain-of-function and loss-of-function mutations of SCN8A in patients with intellectual disabilities and epilepsy. J Med Genet 2015; 52:330-7. [PMID: 25725044 PMCID: PMC4413743 DOI: 10.1136/jmedgenet-2014-102813] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 02/05/2015] [Indexed: 12/19/2022]
Abstract
BACKGROUND Mutations of SCN8A encoding the neuronal voltage-gated sodium channel NaV1.6 are associated with early-infantile epileptic encephalopathy type 13 (EIEE13) and intellectual disability. Using clinical exome sequencing, we have detected three novel de novo SCN8A mutations in patients with intellectual disabilities, and variable clinical features including seizures in two patients. To determine the causality of these SCN8A mutations in the disease of those three patients, we aimed to study the (dys)function of the mutant sodium channels. METHODS The functional consequences of the three SCN8A mutations were assessed using electrophysiological analyses in transfected cells. Genotype-phenotype correlations of these and other cases were related to the functional analyses. RESULTS The first mutant displayed a 10 mV hyperpolarising shift in voltage dependence of activation (gain of function), the second did not form functional channels (loss of function), while the third mutation was functionally indistinguishable from the wildtype channel. CONCLUSIONS Comparison of the clinical features of these patients with those in the literature suggests that gain-of-function mutations are associated with severe EIEE, while heterozygous loss-of-function mutations cause intellectual disability with or without seizures. These data demonstrate that functional analysis of missense mutations detected by clinical exome sequencing, both inherited and de novo, is valuable for clinical interpretation in the age of massive parallel sequencing.
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Affiliation(s)
- Maxime G Blanchard
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marjolein H Willemsen
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Jaclyn B Walker
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Sulayman D Dib-Hajj
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, Connecticut, USA The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Stephen G Waxman
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, Connecticut, USA The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Marjolijn C J Jongmans
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Tjitske Kleefstra
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bart P van de Warrenburg
- Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Peter Praamstra
- Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost Nicolai
- Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands Epilepsy Center Kempenhaeghe, Heeze, The Netherlands
| | - Helger G Yntema
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Erik-Jan Kamsteeg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
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Wagnon JL, Korn MJ, Parent R, Tarpey TA, Jones JM, Hammer MF, Murphy GG, Parent JM, Meisler MH. Convulsive seizures and SUDEP in a mouse model of SCN8A epileptic encephalopathy. Hum Mol Genet 2014; 24:506-15. [PMID: 25227913 PMCID: PMC4275076 DOI: 10.1093/hmg/ddu470] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
De novo mutations of the voltage-gated sodium channel gene SCN8A have recently been recognized as a cause of epileptic encephalopathy, which is characterized by refractory seizures with developmental delay and cognitive disability. We previously described the heterozygous SCN8A missense mutation p.Asn1768Asp in a child with epileptic encephalopathy that included seizures, ataxia, and sudden unexpected death in epilepsy (SUDEP). The mutation results in increased persistent sodium current and hyperactivity of transfected neurons. We have characterized a knock-in mouse model expressing this dominant gain-of-function mutation to investigate the pathology of the altered channel in vivo. The mutant channel protein is stable in vivo. Heterozygous Scn8aN1768D/+ mice exhibit seizures and SUDEP, confirming the causality of the de novo mutation in the proband. Using video/EEG analysis, we detect ictal discharges that coincide with convulsive seizures and myoclonic jerks. Prior to seizure onset, heterozygous mutants are not defective in motor learning or fear conditioning, but do exhibit mild impairment of motor coordination and social discrimination. Homozygous mutant mice exhibit earlier seizure onset than heterozygotes and more rapid progression to death. Analysis of the intermediate phenotype of functionally hemizygous Scn8aN1768D/− mice indicates that severity is increased by a double dose of mutant protein and reduced by the presence of wild-type protein. Scn8aN1768D mutant mice provide a model of epileptic encephalopathy that will be valuable for studying the in vivo effects of hyperactive Nav1.6 and the response to therapeutic interventions.
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Affiliation(s)
| | | | - Rachel Parent
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Taylor A Tarpey
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | | | - Michael F Hammer
- Arizona Research Laboratories, Division of Biotechnology, University of Arizona, Tucson, AZ, USA
| | - Geoffrey G Murphy
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, USA Molecular and Integrative Physiology, University of Michigan Medical Center, Ann Arbor, MI 48109, USA and
| | - Jack M Parent
- Department of Neurology VA Ann Arbor Healthcare System, Ann Arbor, MI, USA
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de Kovel CGF, Meisler MH, Brilstra EH, van Berkestijn FMC, van 't Slot R, van Lieshout S, Nijman IJ, O'Brien JE, Hammer MF, Estacion M, Waxman SG, Dib-Hajj SD, Koeleman BPC. Characterization of a de novo SCN8A mutation in a patient with epileptic encephalopathy. Epilepsy Res 2014; 108:1511-8. [PMID: 25239001 DOI: 10.1016/j.eplepsyres.2014.08.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/19/2014] [Accepted: 08/26/2014] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Recently, de novo SCN8A missense mutations have been identified as a rare dominant cause of epileptic encephalopathies (EIEE13). Functional studies on the first described case demonstrated gain-of-function effects of the mutation. We describe a novel de novo mutation of SCN8A in a patient with epileptic encephalopathy, and functional characterization of the mutant protein. DESIGN Whole exome sequencing was used to discover the variant. We generated a mutant cDNA, transfected HEK293 cells, and performed Western blotting to assess protein stability. To study channel functional properties, patch-clamp experiments were carried out in transfected neuronal ND7/23 cells. RESULTS The proband exhibited seizure onset at 6 months of age, diffuse brain atrophy, and more profound developmental impairment than the original case. The mutation p.Arg233Gly in the voltage sensing transmembrane segment D1S4 was present in the proband and absent in both parents. This mutation results in a temperature-sensitive reduction in protein expression as well as reduced sodium current amplitude and density and a relative increased response to a slow ramp stimulus, though this did not result in an absolute increased current at physiological temperatures. CONCLUSION The new de novo SCN8A mutation is clearly deleterious, resulting in an unstable protein with reduced channel activity. This differs from the gain-of-function attributes of the first SCN8A mutation in epileptic encephalopathy, pointing to heterogeneity of mechanisms. Since Nav1.6 is expressed in both excitatory and inhibitory neurons, a differential effect of a loss-of-function of Nav1.6 Arg223Gly on inhibitory interneurons may underlie the epilepsy phenotype in this patient.
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Affiliation(s)
- Carolien G F de Kovel
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Eva H Brilstra
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Ruben van 't Slot
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Stef van Lieshout
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Isaac J Nijman
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Michael F Hammer
- Arizona Research Laboratories, Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Mark Estacion
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Bobby P C Koeleman
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
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47
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Vaccari I, Carbone A, Previtali SC, Mironova YA, Alberizzi V, Noseda R, Rivellini C, Bianchi F, Del Carro U, D'Antonio M, Lenk GM, Wrabetz L, Giger RJ, Meisler MH, Bolino A. Loss of Fig4 in both Schwann cells and motor neurons contributes to CMT4J neuropathy. Hum Mol Genet 2014; 24:383-96. [PMID: 25187576 PMCID: PMC4275070 DOI: 10.1093/hmg/ddu451] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mutations of FIG4 are responsible for Yunis-Varón syndrome, familial epilepsy with polymicrogyria, and Charcot-Marie-Tooth type 4J neuropathy (CMT4J). Although loss of the FIG4 phospholipid phosphatase consistently causes decreased PtdIns(3,5)P2 levels, cell-specific sensitivity to partial loss of FIG4 function may differentiate FIG4-associated disorders. CMT4J is an autosomal recessive neuropathy characterized by severe demyelination and axonal loss in human, with both motor and sensory involvement. However, it is unclear whether FIG4 has cell autonomous roles in both motor neurons and Schwann cells, and how loss of FIG4/PtdIns(3,5)P2-mediated functions contribute to the pathogenesis of CMT4J. Here, we report that mice with conditional inactivation of Fig4 in motor neurons display neuronal and axonal degeneration. In contrast, conditional inactivation of Fig4 in Schwann cells causes demyelination and defects in autophagy-mediated degradation. Moreover, Fig4-regulated endolysosomal trafficking in Schwann cells is essential for myelin biogenesis during development and for proper regeneration/remyelination after injury. Our data suggest that impaired endolysosomal trafficking in both motor neurons and Schwann cells contributes to CMT4J neuropathy.
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Affiliation(s)
- Ilaria Vaccari
- Division of Neuroscience, INSPE-Institute of Experimental Neurology
| | | | - Stefano Carlo Previtali
- Division of Neuroscience, INSPE-Institute of Experimental Neurology Department of Neurology and
| | | | | | - Roberta Noseda
- Division of Neuroscience, INSPE-Institute of Experimental Neurology
| | | | - Francesca Bianchi
- Division of Neuroscience, INSPE-Institute of Experimental Neurology Department of Neurology and
| | - Ubaldo Del Carro
- Division of Neuroscience, INSPE-Institute of Experimental Neurology Department of Neurology and
| | - Maurizio D'Antonio
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA and
| | - Lawrence Wrabetz
- Hunter James Kelly Research Institute, State University of New York, Buffalo, NY 14203, USA
| | | | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA and
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48
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Estacion M, O'Brien JE, Conravey A, Hammer MF, Waxman SG, Dib-Hajj SD, Meisler MH. A novel de novo mutation of SCN8A (Nav1.6) with enhanced channel activation in a child with epileptic encephalopathy. Neurobiol Dis 2014; 69:117-23. [PMID: 24874546 DOI: 10.1016/j.nbd.2014.05.017] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 04/21/2014] [Accepted: 05/17/2014] [Indexed: 10/25/2022] Open
Abstract
Rare de novo mutations of sodium channels are thought to be an important cause of sporadic epilepsy. The well established role of de novo mutations of sodium channel SCN1A in Dravet Syndrome supports this view, but the etiology of many cases of epileptic encephalopathy remains unknown. We sought to identify the genetic cause in a patient with early onset epileptic encephalopathy by whole exome sequencing of genomic DNA. The heterozygous mutation c. 2003C>T in SCN8A, the gene encoding sodium channel Nav1.6, was detected in the patient but was not present in either parent. The resulting missense substitution, p.Thr767Ile, alters an evolutionarily conserved residue in the first transmembrane segment of channel domain II. The electrophysiological effects of this mutation were assessed in neuronal cells transfected with mutant or wildtype cDNA. The mutation causes enhanced channel activation, with a 10mV depolarizing shift in voltage dependence of activation as well as increased ramp current. In addition, pyramidal hippocampal neurons expressing the mutant channel exhibit increased spontaneous firing with PDS-like complexes as well as increased frequency of evoked action potentials. The identification of this new gain-of-function mutation of Nav1.6 supports the inclusion of SCN8A as a causative gene in infantile epilepsy, demonstrates a novel mechanism for hyperactivity of Nav1.6, and further expands the role of de novo mutations in severe epilepsy.
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Affiliation(s)
- Mark Estacion
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | | | - Michael F Hammer
- ARL Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Stephen G Waxman
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
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49
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Menezes MP, Waddell L, Lenk GM, Kaur S, MacArthur DG, Meisler MH, Clarke NF. Whole exome sequencing identifies three recessive FIG4 mutations in an apparently dominant pedigree with Charcot-Marie-Tooth disease. Neuromuscul Disord 2014; 24:666-70. [PMID: 24878229 DOI: 10.1016/j.nmd.2014.04.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/04/2014] [Accepted: 04/23/2014] [Indexed: 02/07/2023]
Abstract
Charcot-Marie-Tooth disease (CMT) is genetically heterogeneous and classification based on motor nerve conduction velocity and inheritance is used to direct genetic testing. With the less common genetic forms of CMT, identifying the causative genetic mutation by Sanger sequencing of individual genes can be time-consuming and costly. Next-generation sequencing technologies show promise for clinical testing in diseases where a similar phenotype is caused by different genes. We report the unusual occurrence of CMT4J, caused by mutations in FIG4, in a apparently dominant pedigree. The affected proband and her mother exhibit different disease severities associated with different combinations of compound heterozygous FIG4 mutations, identified by whole exome sequencing. The proband was also shown to carry a de novo nonsense mutation in the dystrophin gene, which may contribute to her more severe phenotype. This study is a cautionary reminder that in families with two generations affected, explanations other than dominant inheritance are possible, such as recessive inheritance due to three mutations segregating in the family. It also emphasises the advantages of next-generation sequencing approaches that screen multiple CMT genes at once for patients in whom the common genes have been excluded.
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Affiliation(s)
- Manoj P Menezes
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, Australia.
| | - Leigh Waddell
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, Australia
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Simranpreet Kaur
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia
| | - Daniel G MacArthur
- Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA, USA; Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, MA, USA; Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Nigel F Clarke
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, Australia
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50
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Baulac S, Lenk GM, Dufresnois B, Ouled Amar Bencheikh B, Couarch P, Renard J, Larson PA, Ferguson CJ, Noé E, Poirier K, Hubans C, Ferreira S, Guerrini R, Ouazzani R, El Hachimi KH, Meisler MH, Leguern E. Role of the phosphoinositide phosphatase FIG4 gene in familial epilepsy with polymicrogyria. Neurology 2014; 82:1068-75. [PMID: 24598713 DOI: 10.1212/wnl.0000000000000241] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE The aim of this study was to identify the causal gene in a consanguineous Moroccan family with temporo-occipital polymicrogyria, psychiatric manifestations, and epilepsy, previously mapped to the 6q16-q22 region. METHODS We used exome sequencing and analyzed candidate variants in the 6q16-q22 locus, as well as a rescue assay in Fig4-null mouse fibroblasts and immunohistochemistry of Fig4-null mouse brains. RESULTS A homozygous missense mutation (p.Asp783Val) in the phosphoinositide phosphatase gene FIG4 was identified. Pathogenicity of the variant was supported by impaired rescue of the enlarged vacuoles in transfected fibroblasts from Fig4-deficient mice. Histologic examination of Fig4-null mouse brain revealed neurodevelopmental impairment in the hippocampus, cortex, and cerebellum as well as impaired cerebellar gyration/foliation reminiscent of human cortical malformations. CONCLUSIONS This study extends the spectrum of phenotypes associated with FIG4 mutations to include cortical malformation associated with seizures and psychiatric manifestations, in addition to the previously described Charcot-Marie-Tooth disease type 4J and Yunis-Varón syndrome.
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Affiliation(s)
- Stéphanie Baulac
- From INSERM (S.B., B.D., B.O.A.B., P.C., J.R., E.N., K.H.E.H., E.L.), U1127; Sorbonne Universités, UPMC Univ Paris 06 (S.B., B.D., B.O.A.B., P.C., J.R., E.N., K.H.E.H., E.L.), UM 75; CNRS (S.B., B.D., B.O.A.B., P.C., J.R., E.N., K.H.E.H., E.L.), UMR 7225, ICM, Paris, ICM, (S.B., B.D., B.O.A.B., P.C., J.R., E.N., K.H.E.H., E.L.) Paris, F-75013 Paris, France; Department of Human Genetics (G.M.L., P.A.L., C.J.F., M.H.M.), University of Michigan, Ann Arbor; Service de Neurophysiologie Clinique (B.O.A.B.), Hôpital des Spécialités, Centre Hospitalier Ibn Sina Rabat, Morocco; Genetics and Pathophysiology of Neurodevelopmental and Neuromuscular Diseases (K.P.), Cochin Institute, Paris; GenoScreen (C.H., S.F.), Lille, France; Neuroscience Department (R.G.), Children's Hospital A. Meyer, University of Florence and IRCCS Stella Maris, Pisa, Italy; Laboratoire de Neurogénétique (K.H.E.H.), Ecole Pratique des Hautes Etudes, Paris; and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe hospitalier Pitié-Salpêtrière, Paris, France
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