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Brown SP, Lawson RJ, Moreno JD, Ransdell JL. A Reinterpretation of the Relationship between Persistent and Resurgent Sodium Currents. J Neurosci 2024; 44:e2396232024. [PMID: 38858080 PMCID: PMC11255426 DOI: 10.1523/jneurosci.2396-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/14/2024] [Accepted: 05/31/2024] [Indexed: 06/12/2024] Open
Abstract
The resurgent sodium current (INaR) activates on membrane repolarization, such as during the downstroke of neuronal action potentials. Due to its unique activation properties, INaR is thought to drive high rates of repetitive neuronal firing. However, INaR is often studied in combination with the persistent or noninactivating portion of sodium currents (INaP). We used dynamic clamp to test how INaR and INaP individually affect repetitive firing in adult cerebellar Purkinje neurons from male and female mice. We learned INaR does not scale repetitive firing rates due to its rapid decay at subthreshold voltages and that subthreshold INaP is critical in regulating neuronal firing rate. Adjustments to the voltage-gated sodium conductance model used in these studies revealed INaP and INaR can be inversely scaled by adjusting occupancy in the slow-inactivated kinetic state. Together with additional dynamic clamp experiments, these data suggest the regulation of sodium channel slow inactivation can fine-tune INaP and Purkinje neuron repetitive firing rates.
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Affiliation(s)
- Samuel P Brown
- Department of Biology, Miami University, Oxford, Ohio 45056
| | - Ryan J Lawson
- Department of Biology, Miami University, Oxford, Ohio 45056
| | - Jonathan D Moreno
- Division of Cardiology, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri 63130
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2
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Wong JC, Escayg A. Carvedilol increases seizure resistance in a mouse model of SCN8A-derived epilepsy. Front Pharmacol 2024; 15:1397225. [PMID: 38895634 PMCID: PMC11184058 DOI: 10.3389/fphar.2024.1397225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Accepted: 05/14/2024] [Indexed: 06/21/2024] Open
Abstract
Patients with mutations that alter the function of the sodium channel SCN8A present with a range of clinical features, including mild to severe seizures, developmental delay, intellectual disability, autism, feeding dysfunction, motor impairment, and hypotonia. In an effort to identify compounds that could be potentially beneficial in SCN8A-associated epilepsy, Atkin et al. conducted an in vitro screen which resulted in the identification of 90 compounds that effectively reduced sodium influx into the cells expressing the human SCN8A R1872Q mutation. The top compounds that emerged from this screen included amitriptyline, carvedilol, and nilvadipine. In the current study, we evaluated the ability of these three compounds to increase resistance to 6 Hz or pentylenetetrazole (PTZ)-induced seizures in wild-type CF1 mice and in a mouse line expressing the human SCN8A R1620L mutation. We also evaluated the effects of fenfluramine administration, which was recently associated with a 60%-90% decrease in seizure frequency in three patients with SCN8A-associated epilepsy. While amitriptyline, carvedilol, and fenfluramine provided robust protection against induced seizures in CF1 mice, only carvedilol was able to significantly increase resistance to 6 Hz- and PTZ-induced seizures in RL/+ mutants. These results provide support for further evaluation of carvedilol as a potential treatment for patients with SCN8A mutations.
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Affiliation(s)
- Jennifer C. Wong
- Department of Human Genetics, Emory University, Atlanta, GA, United States
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3
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Brown SP, Lawson RJ, Moreno JD, Ransdell JL. A Reinterpretation of the Relationship Between Persistent and Resurgent Sodium Currents. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.25.564042. [PMID: 38187680 PMCID: PMC10769191 DOI: 10.1101/2023.10.25.564042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
The resurgent sodium current (INaR) activates on membrane repolarization, such as during the downstroke of neuronal action potentials. Due to its unique activation properties, INaR is thought to drive high rates of repetitive neuronal firing. However, INaR is often studied in combination with the persistent or non-inactivating portion of sodium currents (INaP). We used dynamic clamp to test how INaR and INaP individually affect repetitive firing in adult cerebellar Purkinje neurons from male and female mice. We learned INaR does not scale repetitive firing rates due to its rapid decay at subthreshold voltages, and that subthreshold INaP is critical in regulating neuronal firing rate. Adjustments to the Nav conductance model used in these studies revealed INaP and INaR can be inversely scaled by adjusting occupancy in the slow inactivated kinetic state. Together with additional dynamic clamp experiments, these data suggest the regulation of sodium channel slow inactivation can fine-tune INaP and Purkinje neuron repetitive firing rates.
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Affiliation(s)
| | - Ryan J. Lawson
- Department of Biology, Miami University, Oxford, OH 45056
| | - Jonathan D. Moreno
- Division of Cardiology, Department of Medicine, Washington University in St. Louis, St. Louis, MO 63130
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4
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Quinn S, Zhang N, Fenton TA, Brusel M, Muruganandam P, Peleg Y, Giladi M, Haitin Y, Lerche H, Bassan H, Liu Y, Ben-Shalom R, Rubinstein M. Complex biophysical changes and reduced neuronal firing in an SCN8A variant associated with developmental delay and epilepsy. Biochim Biophys Acta Mol Basis Dis 2024; 1870:167127. [PMID: 38519006 DOI: 10.1016/j.bbadis.2024.167127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 03/07/2024] [Accepted: 03/12/2024] [Indexed: 03/24/2024]
Abstract
Mutations in the SCN8A gene, encoding the voltage-gated sodium channel NaV1.6, are associated with a range of neurodevelopmental syndromes. The p.(Gly1625Arg) (G1625R) mutation was identified in a patient diagnosed with developmental epileptic encephalopathy (DEE). While most of the characterized DEE-associated SCN8A mutations were shown to cause a gain-of-channel function, we show that the G1625R variant, positioned within the S4 segment of domain IV, results in complex effects. Voltage-clamp analyses of NaV1.6G1625R demonstrated a mixture of gain- and loss-of-function properties, including reduced current amplitudes, increased time constant of fast voltage-dependent inactivation, a depolarizing shift in the voltage dependence of activation and inactivation, and increased channel availability with high-frequency repeated depolarization. Current-clamp analyses in transfected cultured neurons revealed that these biophysical properties caused a marked reduction in the number of action potentials when firing was driven by the transfected mutant NaV1.6. Accordingly, computational modeling of mature cortical neurons demonstrated a mild decrease in neuronal firing when mimicking the patients' heterozygous SCN8A expression. Structural modeling of NaV1.6G1625R suggested the formation of a cation-π interaction between R1625 and F1588 within domain IV. Double-mutant cycle analysis revealed that this interaction affects the voltage dependence of inactivation in NaV1.6G1625R. Together, our studies demonstrate that the G1625R variant leads to a complex combination of gain and loss of function biophysical changes that result in an overall mild reduction in neuronal firing, related to the perturbed interaction network within the voltage sensor domain, necessitating personalized multi-tiered analysis for SCN8A mutations for optimal treatment selection.
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Affiliation(s)
- Shir Quinn
- Goldschleger Eye Research Institute, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nan Zhang
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Timothy A Fenton
- Neurology Department, MIND Institute, University of California, Davis, Sacramento, CA, United States
| | - Marina Brusel
- Goldschleger Eye Research Institute, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Preethi Muruganandam
- Neurology Department, MIND Institute, University of California, Davis, Sacramento, CA, United States
| | - Yoav Peleg
- Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Moshe Giladi
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Yoni Haitin
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Haim Bassan
- Pediatric Neurology and Development Center, Shamir Medical Center (Assaf Harofeh), Zerifin, Israel; Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany.
| | - Roy Ben-Shalom
- Neurology Department, MIND Institute, University of California, Davis, Sacramento, CA, United States.
| | - Moran Rubinstein
- Goldschleger Eye Research Institute, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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5
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Vanoye CG, Abramova TV, DeKeyser JM, Ghabra NF, Oudin MJ, Burge CB, Helbig I, Thompson CH, George AL. Molecular and cellular context influences SCN8A variant function. JCI Insight 2024; 9:e177530. [PMID: 38771640 DOI: 10.1172/jci.insight.177530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 05/15/2024] [Indexed: 05/23/2024] Open
Abstract
Pathogenic variants in SCN8A, which encodes the voltage-gated sodium (NaV) channel NaV1.6, associate with neurodevelopmental disorders, including developmental and epileptic encephalopathy. Previous approaches to determine SCN8A variant function may be confounded by use of a neonatally expressed, alternatively spliced isoform of NaV1.6 (NaV1.6N) and engineered mutations rendering the channel tetrodotoxin (TTX) resistant. We investigated the impact of SCN8A alternative splicing on variant function by comparing the functional attributes of 15 variants expressed in 2 developmentally regulated splice isoforms (NaV1.6N, NaV1.6A). We employed automated patch clamp recording to enhance throughput, and developed a neuronal cell line (ND7/LoNav) with low levels of endogenous NaV current to obviate the need for TTX-resistance mutations. Expression of NaV1.6N or NaV1.6A in ND7/LoNav cells generated NaV currents with small, but significant, differences in voltage dependence of activation and inactivation. TTX-resistant versions of both isoforms exhibited significant functional differences compared with the corresponding WT channels. We demonstrated that many of the 15 disease-associated variants studied exhibited isoform-dependent functional effects, and that many of the studied SCN8A variants exhibited functional properties that were not easily classified as either gain- or loss-of-function. Our work illustrates the value of considering molecular and cellular context when investigating SCN8A variants.
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Affiliation(s)
- Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Tatiana V Abramova
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Jean-Marc DeKeyser
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Nora F Ghabra
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Madeleine J Oudin
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA
| | - Christopher B Burge
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Ingo Helbig
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Christopher H Thompson
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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6
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Mao M, Mattei C, Rollo B, Byars S, Cuddy C, Berecki G, Heighway J, Pachernegg S, Menheniott T, Apted D, Jia L, Dalby K, Nemiroff A, Mullen S, Reid CA, Maljevic S, Petrou S. Distinctive In Vitro Phenotypes in iPSC-Derived Neurons From Patients With Gain- and Loss-of-Function SCN2A Developmental and Epileptic Encephalopathy. J Neurosci 2024; 44:e0692232023. [PMID: 38148154 PMCID: PMC10883610 DOI: 10.1523/jneurosci.0692-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 11/07/2023] [Accepted: 11/09/2023] [Indexed: 12/28/2023] Open
Abstract
SCN2A encodes NaV1.2, an excitatory neuron voltage-gated sodium channel and a major monogenic cause of neurodevelopmental disorders, including developmental and epileptic encephalopathies (DEE) and autism. Clinical presentation and pharmocosensitivity vary with the nature of SCN2A variant dysfunction and can be divided into gain-of-function (GoF) cases with pre- or peri-natal seizures and loss-of-function (LoF) patients typically having infantile spasms after 6 months of age. We established and assessed patient induced pluripotent stem cell (iPSC) - derived neuronal models for two recurrent SCN2A DEE variants with GoF R1882Q and LoF R853Q associated with early- and late-onset DEE, respectively. Two male patient-derived iPSC isogenic pairs were differentiated using Neurogenin-2 overexpression yielding populations of cortical-like glutamatergic neurons. Functional properties were assessed using patch clamp and multielectrode array recordings and transcriptomic profiles obtained with total mRNA sequencing after 2-4 weeks in culture. At 3 weeks of differentiation, increased neuronal activity at cellular and network levels was observed for R1882Q iPSC-derived neurons. In contrast, R853Q neurons showed only subtle changes in excitability after 4 weeks and an overall reduced network activity after 7 weeks in vitro. Consistent with the reported efficacy in some GoF SCN2A patients, phenytoin (sodium channel blocker) reduced the excitability of neurons to the control levels in R1882Q neuronal cultures. Transcriptomic alterations in neurons were detected for each variant and convergent pathways suggested potential shared mechanisms underlying SCN2A DEE. In summary, patient iPSC-derived neuronal models of SCN2A GoF and LoF pathogenic variants causing DEE show specific functional and transcriptomic in vitro phenotypes.
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Affiliation(s)
- Miaomiao Mao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Cristiana Mattei
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Ben Rollo
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, Victoria 3800, Australia
| | - Sean Byars
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Claire Cuddy
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Geza Berecki
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Jacqueline Heighway
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Svenja Pachernegg
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
- Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria 3052, Australia
| | - Trevelyan Menheniott
- Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria 3052, Australia
| | - Danielle Apted
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Linghan Jia
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Kelley Dalby
- Rogcon Biosciences, Cambridge, MA 02142
- Praxis Precision Medicines, Inc., Cambridge, MA 02142
| | - Alex Nemiroff
- Rogcon Biosciences, Cambridge, MA 02142
- Praxis Precision Medicines, Inc., Cambridge, MA 02142
| | - Saul Mullen
- Austin Health, University of Melbourne, Melbourne, Victoria 3084, Australia
| | - Christopher A Reid
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Snezana Maljevic
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Steven Petrou
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria 3052, Australia
- Praxis Precision Medicines, Inc., Cambridge, MA 02142
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7
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Vanoye CG, Abramova TV, DeKeyser JM, Ghabra NF, Oudin MJ, Burge CB, Helbig I, Thompson CH, George AL. Molecular and Cellular Context Influences SCN8A Variant Function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.11.566702. [PMID: 38014225 PMCID: PMC10680676 DOI: 10.1101/2023.11.11.566702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Pathogenic variants in SCN8A , which encodes the voltage-gated sodium (Na V ) channel Na V 1.6, are associated with neurodevelopmental disorders including epileptic encephalopathy. Previous approaches to determine SCN8A variant function may be confounded by the use of a neonatal-expressed alternatively spliced isoform of Na V 1.6 (Na V 1.6N), and engineered mutations to render the channel tetrodotoxin (TTX) resistant. In this study, we investigated the impact of SCN8A alternative splicing on variant function by comparing the functional attributes of 15 variants expressed in two developmentally regulated splice isoforms (Na V 1.6N, Na V 1.6A). We employed automated patch clamp recording to enhance throughput, and developed a novel neuronal cell line (ND7/LoNav) with low levels of endogenous Na V current to obviate the need for TTX-resistance mutations. Expression of Na V 1.6N or Na V 1.6A in ND7/LoNav cells generated Na V currents that differed significantly in voltage-dependence of activation and inactivation. TTX-resistant versions of both isoforms exhibited significant functional differences compared to the corresponding wild-type (WT) channels. We demonstrated that many of the 15 disease-associated variants studied exhibited isoform-dependent functional effects, and that many of the studied SCN8A variants exhibited functional properties that were not easily classified as either gain- or loss-of-function. Our work illustrates the value of considering molecular and cellular context when investigating SCN8A variants.
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8
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Musto E, Liao VWY, Johannesen KM, Fenger CD, Lederer D, Kothur K, Fisk K, Bennetts B, Vrielynck P, Delaby D, Ceulemans B, Weckhuysen S, Sparber P, Bouman A, Ardern-Holmes S, Troedson C, Battaglia DI, Goel H, Feyma T, Bakhtiari S, Tjoa L, Boxill M, Demina N, Shchagina O, Dadali E, Kruer M, Cantalupo G, Contaldo I, Polster T, Isidor B, Bova SM, Fazeli W, Wouters L, Miranda MJ, Darra F, Pede E, Le Duc D, Jamra RA, Küry S, Proietti J, McSweeney N, Brokamp E, Andrews PI, Gouray Garcia M, Chebib M, Møller RS, Ahring PK, Gardella E. GABRA1-Related Disorders: From Genetic to Functional Pathways. Ann Neurol 2023; 95:27-41. [PMID: 37606373 DOI: 10.1002/ana.26774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 08/18/2023] [Accepted: 08/18/2023] [Indexed: 08/23/2023]
Abstract
OBJECTIVE Variants in GABRA1 have been associated with a broad epilepsy spectrum, ranging from genetic generalized epilepsies to developmental and epileptic encephalopathies. However, our understanding of what determines the phenotype severity and best treatment options remains inadequate. We therefore aimed to analyze the electroclinical features and the functional effects of GABRA1 variants to establish genotype-phenotype correlations. METHODS Genetic and electroclinical data of 27 individuals (22 unrelated and 2 families) harboring 20 different GABRA1 variants were collected and accompanied by functional analysis of 19 variants. RESULTS Individuals in this cohort could be assigned into different clinical subgroups based on the functional effect of their variant and its structural position within the GABRA1 subunit. A homogenous phenotype with mild cognitive impairment and infantile onset epilepsy (focal seizures, fever sensitivity, and electroencephalographic posterior epileptiform discharges) was described for variants in the extracellular domain and the small transmembrane loops. These variants displayed loss-of-function (LoF) effects, and the patients generally had a favorable outcome. A more severe phenotype was associated with variants in the pore-forming transmembrane helices. These variants displayed either gain-of-function (GoF) or LoF effects. GoF variants were associated with severe early onset neurodevelopmental disorders, including early infantile developmental and epileptic encephalopathy. INTERPRETATION Our data expand the genetic and phenotypic spectrum of GABRA1 epilepsies and permit delineation of specific subphenotypes for LoF and GoF variants, through the heterogeneity of phenotypes and variants. Generally, variants in the transmembrane helices cause more severe phenotypes, in particular GoF variants. These findings establish the basis for a better understanding of the pathomechanism and a precision medicine approach in GABRA1-related disorders. Further studies in larger populations are needed to provide a conclusive genotype-phenotype correlation. ANN NEUROL 2023.
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Affiliation(s)
- Elisa Musto
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Dianalund, Denmark
- Pediatric Neurology, Department of Woman and Child Health and Public Health, Child Health Area, Catholic University UCSC, Rome, Italy
- Epilepsy and Movement Disorder Neurology, Ospedale Pediatrico Bambino Gesù IRCCS, Rome, Italy
| | - Vivian W Y Liao
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Katrine M Johannesen
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Dianalund, Denmark
- Department of Genetics, University Hospital of Copenhagen, Copenhagen, Denmark
| | - Christina D Fenger
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Dianalund, Denmark
- Amplexa Genetics, Odense, Denmark
| | - Damien Lederer
- Center for Human Genetics, Institut de Pathologie et de Génétique, Gosselies, Belgium
| | - Kavitha Kothur
- Kids Neuroscience Centre, Children's Hospital at Westmead, University of Sydney, Sydney, New South Wales, Australia
| | - Katrina Fisk
- Sydney Genome Diagnostics, Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Bruce Bennetts
- Sydney Genome Diagnostics, Western Sydney Genetics Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia
- Specialty of Genomic Medicine, Children's Hospital at Westmead Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Pascal Vrielynck
- Reference Center for Refractory Epilepsy, Catholic University of Louvain, William Lennox Neurological Hospital, Ottignies, Belgium
| | - Delphine Delaby
- Reference Center for Refractory Epilepsy, Catholic University of Louvain, William Lennox Neurological Hospital, Ottignies, Belgium
| | - Berten Ceulemans
- Department of Pediatric Neurology, Antwerp University Hospital, University of Antwerp, Antwerp, Belgium
| | - Sarah Weckhuysen
- Applied & Translational Neurogenomics Group, VIB-Department of Molecular Genetics, University of Antwerp, Antwerp, Belgium
- Department of Neurology, Antwerp University Hospital, Antwerp, Belgium
- Translational Neurosciences, Faculty of Medicine and Health Science, University of Antwerp, Antwerp, Belgium
| | - Peter Sparber
- Research Center for Medical Genetics Moskvorechie 1, Moscow, Russia
| | - Arjan Bouman
- Department of Clinical Genetics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Simone Ardern-Holmes
- Kids Neuroscience Centre, Children's Hospital at Westmead, University of Sydney, Sydney, New South Wales, Australia
- T. Y. Nelson Department of Neurology and Neurosurgery, Children's Hospital at Westmead, Westmead, New South Wales, Australia
| | - Christopher Troedson
- T. Y. Nelson Department of Neurology and Neurosurgery, Children's Hospital at Westmead, Westmead, New South Wales, Australia
| | - Domenica I Battaglia
- Pediatric Neurology, Department of Woman and Child Health and Public Health, Child Health Area, Catholic University UCSC, Rome, Italy
| | - Himanshu Goel
- Hunter Genetics, Newcastle, New South Wales, Australia
| | - Timothy Feyma
- Gillette Children's Specialty Healthcare, Saint Paul, MN, USA
| | - Somayeh Bakhtiari
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
- Departments of Child Health, Neurology, and Cellular & Molecular Medicine and Program in Genetics, University of Arizona College of Medicine, Phoenix, AZ, USA
| | - Linda Tjoa
- Townsville University Hospital, Douglas, Queensland, Australia
| | - Martin Boxill
- Department of Pediatrics, Viborg Regional Hospital, Viborg, Denmark
| | - Nina Demina
- Research Center for Medical Genetics Moskvorechie 1, Moscow, Russia
| | - Olga Shchagina
- Research Center for Medical Genetics Moskvorechie 1, Moscow, Russia
| | - Elena Dadali
- Research Center for Medical Genetics Moskvorechie 1, Moscow, Russia
| | - Michael Kruer
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
- Departments of Child Health, Neurology, and Cellular & Molecular Medicine and Program in Genetics, University of Arizona College of Medicine, Phoenix, AZ, USA
| | - Gaetano Cantalupo
- Child Neuropsychiatry Section, Department of Surgical Sciences, Dentistry, Gynecology and Paediatrics, University of Verona, Verona, Italy
- UOC Neuropsichiatria Infantile, Dipartimento Materno-Infantile, Azienda Ospedaliero-Universitaria Integrata (full member of the ERN EpiCare), Verona, Italy
- Center for Research on Epilepsies in Pediatric age (CREP), Verona, Italy
| | - Ilaria Contaldo
- Pediatric Neurology, Department of Woman and Child Health and Public Health, Child Health Area, Catholic University UCSC, Rome, Italy
| | - Tilman Polster
- Department of Epileptology (Krankenhaus Mara), Bielefeld University Medical School, Bielefeld, Germany
| | | | - Stefania M Bova
- Pediatric Neurology Unit, V. Buzzi Children's Hospital, Milan, Italy
| | - Walid Fazeli
- Department of Neuropediatrics, Children's Hospital, University of Bonn, Bonn, Germany
| | - Leen Wouters
- Department of Pediatrics, Ziekenhuis Oost-Limburg, Genk, Belgium
| | - Maria J Miranda
- Department of Pediatrics, Pediatric Neurology, Herlev University Hospital, Copenhagen University, Herlev, Denmark
| | - Francesca Darra
- Child Neuropsychiatry Section, Department of Surgical Sciences, Dentistry, Gynecology and Paediatrics, University of Verona, Verona, Italy
- UOC Neuropsichiatria Infantile, Dipartimento Materno-Infantile, Azienda Ospedaliero-Universitaria Integrata (full member of the ERN EpiCare), Verona, Italy
- Center for Research on Epilepsies in Pediatric age (CREP), Verona, Italy
| | - Elisa Pede
- Pediatric Neurology, Department of Woman and Child Health and Public Health, Child Health Area, Catholic University UCSC, Rome, Italy
| | - Diana Le Duc
- Department of Human Genetics, University of Leipzig Faculty of Medicine, Leipzig, Germany
| | - Rami Abou Jamra
- Department of Human Genetics, University of Leipzig Faculty of Medicine, Leipzig, Germany
| | - Sébastien Küry
- Service de Génétique Médicale, CHU Nantes, Nantes, France
- l'Institut du Thorax, INSERM, CNRS, Université de Nantes, Nantes, France
| | - Jacopo Proietti
- Child Neuropsychiatry Section, Department of Surgical Sciences, Dentistry, Gynecology and Paediatrics, University of Verona, Verona, Italy
- Irish Centre for Fetal and Neonatal Translational Research, Child Neuropsychiatry, Cork, Ireland
| | - Niamh McSweeney
- Department of Paediatrics, Cork University Hospital, Cork, Ireland
| | - Elly Brokamp
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Peter Ian Andrews
- Department of Neurology, Sydney Children's Hospital, Randwick, New South Wales, Australia
| | | | - Mary Chebib
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Dianalund, Denmark
- Department of Regional Health Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
| | - Philip K Ahring
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Dianalund, Denmark
- Department of Regional Health Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
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9
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Clatot J, Parthasarathy S, Cohen S, McKee J, Massey S, Somarowthu A, Goldberg EM, Helbig I. SCN1A gain-of-function mutation causing an early onset epileptic encephalopathy. Epilepsia 2023; 64:1318-1330. [PMID: 36287100 PMCID: PMC10130239 DOI: 10.1111/epi.17444] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 10/21/2022] [Accepted: 10/21/2022] [Indexed: 01/19/2023]
Abstract
OBJECTIVE Loss-of-function variants in SCN1A cause Dravet syndrome, the most common genetic developmental and epileptic encephalopathy (DEE). However, emerging evidence suggests separate entities of SCN1A-related disorders due to gain-of-function variants. Here, we aim to refine the clinical, genetic, and functional electrophysiological features of a recurrent p.R1636Q gain-of-function variant, identified in four individuals at a single center. METHODS Individuals carrying the recurrent SCN1A p.R1636Q variant were identified through diagnostic testing. Whole cell voltage-clamp electrophysiological recording in HEK-293 T cells was performed to compare the properties of sodium channels containing wild-type Nav 1.1 or Nav 1.1-R1636Q along with both Nav β1 and Nav β2 subunits, including response to oxcarbazepine. To delineate differences from other SCN1A-related epilepsies, we analyzed electronic medical records. RESULTS All four individuals had an early onset DEE characterized by focal tonic seizures and additional seizure types starting in the first few weeks of life. Electrophysiological analysis showed a mixed gain-of-function effect with normal current density, a leftward (hyperpolarized) shift of steady-state inactivation, and slower inactivation kinetics leading to a prominent late sodium current. The observed functional changes closely paralleled effects of pathogenic variants in SCN3A and SCN8A at corresponding positions. Both wild type and variant exhibited sensitivity to block by oxcarbazepine, partially correcting electrophysiological abnormalities of the SCN1A p.R1636Q variant. Clinically, a single individual responded to treatment with oxcarbazepine. Across 51 individuals with SCN1A-related epilepsies, those with the recurrent p.R1636Q variants had the earliest ages at onset. SIGNIFICANCE The recurrent SCN1A p.R1636Q variant causes a clinical entity with a wider clinical spectrum than previously reported, characterized by neonatal onset epilepsy and absence of prominent movement disorder. Functional consequences of this variant lead to mixed loss and gain of function that is partially corrected by oxcarbazepine. The recurrent p.R1636Q variant represents one of the most common causes of early onset SCN1A-related epilepsies with separate treatment and prognosis implications.
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Affiliation(s)
- Jérôme Clatot
- Division of Neurology, Department of Pediatrics
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | - Shridhar Parthasarathy
- Division of Neurology, Department of Pediatrics
- Department of Biomedical Health Informatics (DBHi)
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | - Stacey Cohen
- Division of Neurology, Department of Pediatrics
- Department of Biomedical Health Informatics (DBHi)
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | - Jillian McKee
- Division of Neurology, Department of Pediatrics
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | - Shavonne Massey
- Division of Neurology, Department of Pediatrics
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | | | - Ethan M. Goldberg
- Division of Neurology, Department of Pediatrics
- Department of Biomedical Health Informatics (DBHi)
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, USA
| | - Ingo Helbig
- Division of Neurology, Department of Pediatrics
- Department of Biomedical Health Informatics (DBHi)
- The Epilepsy NeuroGenetics Initiative, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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10
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Wong JC. Gaining Awareness of Increasingly Persistent SCN1A Mutations. Epilepsy Curr 2023. [DOI: 10.1177/15357597231157484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023] Open
Abstract
[Box: see text]
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11
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Structure of human Na V1.6 channel reveals Na + selectivity and pore blockade by 4,9-anhydro-tetrodotoxin. Nat Commun 2023; 14:1030. [PMID: 36823201 PMCID: PMC9950489 DOI: 10.1038/s41467-023-36766-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 02/15/2023] [Indexed: 02/25/2023] Open
Abstract
The sodium channel NaV1.6 is widely expressed in neurons of the central and peripheral nervous systems, which plays a critical role in regulating neuronal excitability. Dysfunction of NaV1.6 has been linked to epileptic encephalopathy, intellectual disability and movement disorders. Here we present cryo-EM structures of human NaV1.6/β1/β2 alone and complexed with a guanidinium neurotoxin 4,9-anhydro-tetrodotoxin (4,9-ah-TTX), revealing molecular mechanism of NaV1.6 inhibition by the blocker. The apo-form structure reveals two potential Na+ binding sites within the selectivity filter, suggesting a possible mechanism for Na+ selectivity and conductance. In the 4,9-ah-TTX bound structure, 4,9-ah-TTX binds to a pocket similar to the tetrodotoxin (TTX) binding site, which occupies the Na+ binding sites and completely blocks the channel. Molecular dynamics simulation results show that subtle conformational differences in the selectivity filter affect the affinity of TTX analogues. Taken together, our results provide important insights into NaV1.6 structure, ion conductance, and inhibition.
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12
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Guo QB, Zhan L, Xu HY, Gao ZB, Zheng YM. SCN8A epileptic encephalopathy mutations display a gain-of-function phenotype and divergent sensitivity to antiepileptic drugs. Acta Pharmacol Sin 2022; 43:3139-3148. [PMID: 35902765 PMCID: PMC9712530 DOI: 10.1038/s41401-022-00955-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 07/05/2022] [Indexed: 11/09/2022] Open
Abstract
De novo missense mutations in SCN8A gene encoding voltage-gated sodium channel NaV1.6 are linked to a severe form of early infantile epileptic encephalopathy named early infantile epileptic encephalopathy type13 (EIEE13). The majority of the patients with EIEE13 does not respond favorably to the antiepileptic drugs (AEDs) in clinic and has a significantly increased risk of death. Although more than 60 EIEE13-associated mutations have been discovered, only few mutations have been functionally analyzed. In this study we investigated the functional influences of mutations N1466T and N1466K, two EIEE13-associated mutations located in the inactivation gate, on sodium channel properties. Sodium currents were recorded from CHO cells expressing the mutant and wide-type (WT) channels using the whole-cell patch-clamp technique. We found that, in comparison with WT channels, both the mutant channels exhibited increased window currents, persistent currents (INaP) and ramp currents, suggesting that N1466T and N1466K were gain-of-function (GoF) mutations. Sodium channel inhibition is one common mechanism of currently available AEDs, in which topiramate (TPM) was effective in controlling seizures of patients carrying either of the two mutations. We found that TPM (100 µM) preferentially inhibited INaP and ramp currents but did not affect transient currents (INaT) mediated by N1466T or N1466K. Among the other 6 sodium channel-inhibiting AEDs tested, phenytoin and carbamazepine displayed greater efficacy than TPM in suppressing both INaP and ramp currents. Functional characterization of mutants N1466T and N1466K is beneficial for understanding the pathogenesis of EIEE13. The divergent effects of sodium channel-inhibiting AEDs on INaP and ramp currents provide insight into the development of therapeutic strategies for the N1466T and N1466K-associated EIEE13.
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Affiliation(s)
- Qian-Bei Guo
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Li Zhan
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Hai-Yan Xu
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Zhao-Bing Gao
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zhongshan, 528437, China.
| | - Yue-Ming Zheng
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
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13
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Ressler AK, Goldstein DB. Using reported pathogenic variants to identify therapeutic opportunities for genetic diseases. Mol Genet Genomic Med 2022; 11:e2097. [PMID: 36374045 PMCID: PMC9834146 DOI: 10.1002/mgg3.2097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 11/03/2022] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Drug development strategies for genetic diseases depend critically on accurate knowledge of how pathogenic variants cause disease. For some well-studied genes, the direct effects of pathogenic variants are well documented as loss-of-function, gain-of-function or hypermorphic, or a combination of the two. For many genes, however, even the direction of effect of variants remains unclear. Classification of Mendelian disease genes in terms of whether pathogenic variants are loss- or gain-of-function would directly inform drug development strategies. METHODS We leveraged the recent dramatic increase in reported pathogenic variants to provide a novel approach to inferring the direction of effect of pathogenic variants. Specifically, we quantify the ratio of reported pathogenic variants that are missense compared to loss-of-function. RESULTS We first show that for many genes that cause dominant Mendelian disease, the ratio of reported pathogenic missense variants is diagnostic of whether the gene causes disease through loss- or gain-of-function, or a combination. Second, we identify a set of genes that appear to cause disease largely or entirely through gain-of-function or hypermorphic pathogenic variants. CONCLUSIONS We suggest a set of 16 genes suitable for drug developmental efforts utilizing direct inhibition.
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Affiliation(s)
- Andrew K. Ressler
- Institute for Genomic MedicineColumbia UniversityNew YorkNew YorkUSA
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14
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Johannesen KM, Liu Y, Koko M, Gjerulfsen CE, Sonnenberg L, Schubert J, Fenger CD, Eltokhi A, Rannap M, Koch NA, Lauxmann S, Krüger J, Kegele J, Canafoglia L, Franceschetti S, Mayer T, Rebstock J, Zacher P, Ruf S, Alber M, Sterbova K, Lassuthová P, Vlckova M, Lemke JR, Platzer K, Krey I, Heine C, Wieczorek D, Kroell-Seger J, Lund C, Klein KM, Au PYB, Rho JM, Ho AW, Masnada S, Veggiotti P, Giordano L, Accorsi P, Hoei-Hansen CE, Striano P, Zara F, Verhelst H, Verhoeven JS, Braakman HMH, van der Zwaag B, Harder AVE, Brilstra E, Pendziwiat M, Lebon S, Vaccarezza M, Le NM, Christensen J, Grønborg S, Scherer SW, Howe J, Fazeli W, Howell KB, Leventer R, Stutterd C, Walsh S, Gerard M, Gerard B, Matricardi S, Bonardi CM, Sartori S, Berger A, Hoffman-Zacharska D, Mastrangelo M, Darra F, Vøllo A, Motazacker MM, Lakeman P, Nizon M, Betzler C, Altuzarra C, Caume R, Roubertie A, Gélisse P, Marini C, Guerrini R, Bilan F, Tibussek D, Koch-Hogrebe M, Perry MS, Ichikawa S, Dadali E, Sharkov A, Mishina I, Abramov M, Kanivets I, Korostelev S, Kutsev S, Wain KE, Eisenhauer N, Wagner M, Savatt JM, Müller-Schlüter K, Bassan H, Borovikov A, Nassogne MC, Destrée A, Schoonjans AS, Meuwissen M, Buzatu M, Jansen A, Scalais E, Srivastava S, Tan WH, Olson HE, Loddenkemper T, Poduri A, Helbig KL, Helbig I, Fitzgerald MP, Goldberg EM, Roser T, Borggraefe I, Brünger T, May P, Lal D, Lederer D, Rubboli G, Heyne HO, Lesca G, Hedrich UBS, Benda J, Gardella E, Lerche H, Møller RS. Genotype-phenotype correlations in SCN8A-related disorders reveal prognostic and therapeutic implications. Brain 2022; 145:2991-3009. [PMID: 34431999 PMCID: PMC10147326 DOI: 10.1093/brain/awab321] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 06/24/2021] [Accepted: 07/22/2021] [Indexed: 11/13/2022] Open
Abstract
We report detailed functional analyses and genotype-phenotype correlations in 392 individuals carrying disease-causing variants in SCN8A, encoding the voltage-gated Na+ channel Nav1.6, with the aim of describing clinical phenotypes related to functional effects. Six different clinical subgroups were identified: Group 1, benign familial infantile epilepsy (n = 15, normal cognition, treatable seizures); Group 2, intermediate epilepsy (n = 33, mild intellectual disability, partially pharmaco-responsive); Group 3, developmental and epileptic encephalopathy (n = 177, severe intellectual disability, majority pharmaco-resistant); Group 4, generalized epilepsy (n = 20, mild to moderate intellectual disability, frequently with absence seizures); Group 5, unclassifiable epilepsy (n = 127); and Group 6, neurodevelopmental disorder without epilepsy (n = 20, mild to moderate intellectual disability). Those in Groups 1-3 presented with focal or multifocal seizures (median age of onset: 4 months) and focal epileptiform discharges, whereas the onset of seizures in patients with generalized epilepsy was later (median: 42 months) with generalized epileptiform discharges. We performed functional studies expressing missense variants in ND7/23 neuroblastoma cells and primary neuronal cultures using recombinant tetrodotoxin-insensitive human Nav1.6 channels and whole-cell patch-clamping. Two variants causing developmental and epileptic encephalopathy showed a strong gain-of-function (hyperpolarizing shift of steady-state activation, strongly increased neuronal firing rate) and one variant causing benign familial infantile epilepsy or intermediate epilepsy showed a mild gain-of-function (defective fast inactivation, less increased firing). In contrast, all three variants causing generalized epilepsy induced a loss-of-function (reduced current amplitudes, depolarizing shift of steady-state activation, reduced neuronal firing). Functional effects were known for 170 individuals. All 136 individuals carrying a functionally tested gain-of-function variant had either focal (n = 97, Groups 1-3) or unclassifiable (n = 39) epilepsy, whereas 34 individuals with a loss-of-function variant had either generalized (n = 14), no (n = 11) or unclassifiable (n = 6) epilepsy; only three had developmental and epileptic encephalopathy. Computational modelling in the gain-of-function group revealed a significant correlation between the severity of the electrophysiological and clinical phenotypes. Gain-of-function variant carriers responded significantly better to sodium channel blockers than to other anti-seizure medications, and the same applied for all individuals in Groups 1-3. In conclusion, our data reveal clear genotype-phenotype correlations between age at seizure onset, type of epilepsy and gain- or loss-of-function effects of SCN8A variants. Generalized epilepsy with absence seizures is the main epilepsy phenotype of loss-of-function variant carriers and the extent of the electrophysiological dysfunction of the gain-of-function variants is a main determinant of the severity of the clinical phenotype in focal epilepsies. Our pharmacological data indicate that sodium channel blockers present a treatment option in SCN8A-related focal epilepsy with onset in the first year of life.
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Affiliation(s)
- Katrine M Johannesen
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
- Institute for Regional Health Services, University of Southern Denmark, 5230 Odense, Denmark
| | - Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Mahmoud Koko
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Cathrine E Gjerulfsen
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
| | - Lukas Sonnenberg
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
- Institute for Neurobiology, University of Tuebingen, 72072 Tuebingen, Germany
| | - Julian Schubert
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Christina D Fenger
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
| | - Ahmed Eltokhi
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Maert Rannap
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Nils A Koch
- Institute for Neurobiology, University of Tuebingen, 72072 Tuebingen, Germany
| | - Stephan Lauxmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
- Institute for Neurobiology, University of Tuebingen, 72072 Tuebingen, Germany
| | - Johanna Krüger
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Josua Kegele
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Laura Canafoglia
- Department of Diagnostics and Technology, Fondazione IRCCS Istituto Neurologio Carlo Besta, 20125 Milan, Italy
| | - Silvana Franceschetti
- Department of Diagnostics and Technology, Fondazione IRCCS Istituto Neurologio Carlo Besta, 20125 Milan, Italy
| | - Thomas Mayer
- Epilepsy Center Kleinwachau, 01454 Dresden-Radeberg, Germany
| | | | - Pia Zacher
- Epilepsy Center Kleinwachau, 01454 Dresden-Radeberg, Germany
| | - Susanne Ruf
- Department of Pediatric Neurology and Developmental Medicine, University Children’s Hospital, 72072 Tuebingen, Germany
| | - Michael Alber
- Department of Pediatric Neurology and Developmental Medicine, University Children’s Hospital, 72072 Tuebingen, Germany
| | - Katalin Sterbova
- Department of Child Neurology, 2nd Faculty of Medicine, Charles University and University Hospital Motol, 10000 Prague, Czech Republic
| | - Petra Lassuthová
- Department of Child Neurology, 2nd Faculty of Medicine, Charles University and University Hospital Motol, 10000 Prague, Czech Republic
| | - Marketa Vlckova
- Department of Child Neurology, 2nd Faculty of Medicine, Charles University and University Hospital Motol, 10000 Prague, Czech Republic
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, 4275 Leipzig, Germany
| | - Konrad Platzer
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, 4275 Leipzig, Germany
| | - Ilona Krey
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, 4275 Leipzig, Germany
| | - Constanze Heine
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, 4275 Leipzig, Germany
| | - Dagmar Wieczorek
- Institute of Human Genetics, University Clinic, Heinrich-Heine-University, 40210 Düsseldorf, Germany
| | - Judith Kroell-Seger
- Children’s Department, Swiss Epilepsy Centre, Clinic Lengg, 8001 Zurich, Switzerland
| | - Caroline Lund
- National Centre for Rare Epilepsy-Related Disorders, Oslo University Hospital, 0001 Oslo, Norway
| | - Karl Martin Klein
- Departments of Clinical Neurosciences, Medical Genetics and Community Health Sciences, Hotchkiss Brain Institute and Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2P 0A1, Canada
| | - P Y Billie Au
- Department of Medical Genetics, Alberta Children’s Hospital Research Institute, University of Calgary, AB T6G 2T4, Canada
| | - Jong M Rho
- Section of Pediatric Neurology, Alberta Children’s Hospital, Cumming School of Medicine, University of Calgary, Calgary, AB T2P 0A1, Canada
| | - Alice W Ho
- Section of Pediatric Neurology, Alberta Children’s Hospital, Cumming School of Medicine, University of Calgary, Calgary, AB T2P 0A1, Canada
| | - Silvia Masnada
- Department of Child Neurology, V. Buzzi Children’s Hospital, 20125 Milan, Italy
| | - Pierangelo Veggiotti
- Department of Child Neurology, V. Buzzi Children’s Hospital, 20125 Milan, Italy
- ‘L. Sacco’ Department of Biomedical and Clinical Sciences, University of Milan, 20157 Milan, Italy
| | - Lucio Giordano
- Child Neuropsychiatric Unit, Civilian Hospital, 25100 Brescia, Italy
| | - Patrizia Accorsi
- Child Neuropsychiatric Unit, Civilian Hospital, 25100 Brescia, Italy
| | - Christina E Hoei-Hansen
- Department of Pediatrics, Copenhagen University Hospital Rigshospitalet, 2200 Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Pasquale Striano
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16121 Genova, Italy
- IRCCS ‘G. Gaslini’ Institute, 16121 Genoa, Italy
| | | | - Helene Verhelst
- Department of Pediatrics, Division of Pediatric Neurology, Gent University Hospital, 9042 Gent, Belgium
| | - Judith S Verhoeven
- Academic Center for Epileptology, Kempenhaeghe/Maastricht University Medical Center, 5591 Heeze, The Netherlands
| | - Hilde M H Braakman
- Department of Pediatric Neurology, Amalia Children’s Hospital, Radboud University Medical Center, 6525 Nijmegen, The Netherlands
| | - Bert van der Zwaag
- Department of Genetics, University Medical Center Utrecht, Utrecht University, 3553 Utrecht, The Netherlands
| | - Aster V E Harder
- Department of Genetics, University Medical Center Utrecht, Utrecht University, 3553 Utrecht, The Netherlands
| | - Eva Brilstra
- Department of Genetics, University Medical Center Utrecht, Utrecht University, 3553 Utrecht, The Netherlands
| | - Manuela Pendziwiat
- Department of Neuropediatrics, Universitätsklinikum Schleswig Holstein Campus Kiel, 24106 Kiel, Germany
| | - Sebastian Lebon
- Pediatric Neurology and Neurorehabilitation Unit, Woman Mother Child Department, Lausanne University Hospital (CHUV), 1000 Lausanne, Switzerland
- University of Lausanne, 1000 Lausanne, Switzerland
| | - Maria Vaccarezza
- Department of Pediatric Neurology, Hospital Italiano de Buenos Aires, C1428 Buenos Aires, Argentina
| | - Ngoc Minh Le
- Center for Pediatric Neurology, Cleveland Clinic, Cleveland, OH 44102, USA
| | - Jakob Christensen
- Department of Neurology, Aarhus University Hospital, 8000 Aarhus, Denmark
| | - Sabine Grønborg
- Center for Rare Diseases, Department of Pediatrics and Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, 2200 Copenhagen, Denmark
| | - Stephen W Scherer
- McLaughlin Centre and Department of Molecular Genetics, University of Toronto, Toronto, ON 66777, Canada
- The Centre for Applied Genomics and Department of Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON 66777, Canada
| | - Jennifer Howe
- Department of Neuropediatrics, University Hospital Bonn, 53229 Bonn, Germany
| | - Walid Fazeli
- Institute for Molecular and Behavioral Neuroscience, University of Cologne, 50667 Cologne, Germany
- Neurology Department, The Royal Children’s Hospital Melbourne, 3002 Melbourne, Australia
| | - Katherine B Howell
- Neurology Department, The Royal Children’s Hospital Melbourne, 3002 Melbourne, Australia
- Murdoch Children’s Research Institute, 3052 Parkville, Australia
- Department of Pediatrics, University of Melbourne, Royal Children’s Hospital, 3052 Parkville, Australia
| | - Richard Leventer
- Neurology Department, The Royal Children’s Hospital Melbourne, 3002 Melbourne, Australia
- Murdoch Children’s Research Institute, 3052 Parkville, Australia
- Department of Pediatrics, University of Melbourne, Royal Children’s Hospital, 3052 Parkville, Australia
| | - Chloe Stutterd
- Murdoch Children’s Research Institute, 3052 Parkville, Australia
- Department of Pediatrics, University of Melbourne, Royal Children’s Hospital, 3052 Parkville, Australia
| | - Sonja Walsh
- Department of Neuropediatrics, Children’s Hospital, University Hospital Carl Gustav Carus, Technical University, 1099 Dresden, Germany
| | - Marion Gerard
- Genetics Department, CHU Côte de Nacre, 14118 Caen, France
| | | | - Sara Matricardi
- Child Neurology and Psychiatry Unit, Children’s Hospital G. Salesi, 60121 Ancona, Italy
| | - Claudia M Bonardi
- Department of Woman’s and Child’s Health, Padova University Hospital, 35100 Padova, Italy
| | - Stefano Sartori
- Child Neurology and Clinical Neurophysiology Unit, Padova University Hospital, 35100 Padova, Italy
| | - Andrea Berger
- Department of Neuropediatrics, Klinikum Weiden, Kliniken Nordoberpfalz AG, 92637 Weiden, Germany
| | | | - Massimo Mastrangelo
- Pediatric Neurology Unit, Vittore Buzzi Hospital, ASST Fatebenefratelli Sacco, 20100 Milan, Italy
| | - Francesca Darra
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, 37121 Verona, Italy
| | - Arve Vøllo
- Department of Pediatrics, Oestfold Hospital, 1712 Graalum, Norway
| | - M Mahdi Motazacker
- Laboratory of Genome Diagnostics, Department of Clinical Genetics, Amsterdam UMC, University of Amsterdam, 1019 Amsterdam, Netherlands
| | - Phillis Lakeman
- Department of Clinical Genetics, Amsterdam Reproduction and Development Research Institute, Amsterdam UMC, University of Amsterdam, 1019 Amsterdam, Netherlands
| | - Mathilde Nizon
- Service de Génétique Médicale, CHU Nantes, 44093 Nantes, France
| | - Cornelia Betzler
- Clinic for Neuropediatrics and Neurorehabilitation, Epilepsy Center for Children and Adolescents, Schön Klinik, 83569 Vogtareuth, Germany
- Research Institute ‘Rehabilitation, Transition, Palliation’, PMU Salzburg, 5020 Salzburg, Austria
| | - Cecilia Altuzarra
- Department of Pediatrics, St. Jacques Hospital, 25000 Besançon, France
| | - Roseline Caume
- Clinique de Génétique Guy Fontaine, CHU Lille, 59000, Lille, France
| | - Agathe Roubertie
- Département de Neuropédiatrie, INSERM, CHU Montpellier, 34000 Montpellier, France
| | - Philippe Gélisse
- Département de Neuropédiatrie, INSERM, CHU Montpellier, 34000 Montpellier, France
| | - Carla Marini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children’s Hospital, University of Florence, 50131 Florence, Italy
| | | | - Frederic Bilan
- Service de Génétique, Centre Hospitalier Universitaire de Poitiers, 86021 Poitiers, France
| | - Daniel Tibussek
- Child Neurology, Center for Pediatric and Teenage Health Care, 53757 Sankt Augustin, Germany
| | | | - M Scott Perry
- Justin Neurosciences Center, Cook Children’s Medical Center, Fort Worth, TX 76101, USA
| | - Shoji Ichikawa
- Department of Clinical Diagnostics, Ambry Genetics, Aliso Viejo, CA 92637, USA
| | - Elena Dadali
- Research Centre for Medical Genetics, 115522 Moscow, Russia
- Veltischev Research and Clinical Institute for Pediatrics, Pirogov Russian National Research Medical University, 125412 Moscow, Russia
| | - Artem Sharkov
- Veltischev Research and Clinical Institute for Pediatrics, Pirogov Russian National Research Medical University, 125412 Moscow, Russia
- Genomed Ltd., 100000 Moscow, Russia
| | - Irina Mishina
- Research Centre for Medical Genetics, 115522 Moscow, Russia
| | - Mikhail Abramov
- Veltischev Research and Clinical Institute for Pediatrics, Pirogov Russian National Research Medical University, 125412 Moscow, Russia
| | - Ilya Kanivets
- Svt. Luka’s Institute of Child Neurology & Epilepsy, 100000 Moscow, Russia
- Russian Medical Academy of Continuous Professional Education, 100000 Moscow, Russia
| | - Sergey Korostelev
- Svt. Luka’s Institute of Child Neurology & Epilepsy, 100000 Moscow, Russia
- I.M. Sechenov First Moscow State Medical University, 100000 Moscow, Russia
| | - Sergey Kutsev
- Research Centre for Medical Genetics, 115522 Moscow, Russia
| | - Karen E Wain
- Geisinger Autism & Developmental Medicine Institute, Lewisburg, PA 17837, USA
| | - Nancy Eisenhauer
- Geisinger Autism & Developmental Medicine Institute, Lewisburg, PA 17837, USA
| | - Monisa Wagner
- Geisinger Autism & Developmental Medicine Institute, Lewisburg, PA 17837, USA
| | - Juliann M Savatt
- Geisinger Autism & Developmental Medicine Institute, Lewisburg, PA 17837, USA
| | - Karen Müller-Schlüter
- Epilepsy Center for Children, University Hospital Neuruppin, Brandenburg Medical School, 16816 Neuruppin, Germany
| | - Haim Bassan
- Pediatric Neurology & Development Center, Shamir Medical Center (Assaf Harofe), Be'er Ya'akov, Israel
- Sackler Faculty of Medicine, Tel Aviv University, 5296001 Tel Aviv, Israel
| | | | - Marie Cecile Nassogne
- Pediatric Neurology Unit, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, 1000 Brussels, Belgium
| | - Anne Destrée
- Institute for Pathology and Genetics, 6040 Gosselies, Belgium
| | - An Sofie Schoonjans
- Department of Pediatrics and Pediatric Neurology, Antwerp University Hospital, University of Antwerp, 2650 Edegem, Belgium
| | - Marije Meuwissen
- Pediatric Neurology, Marie Curie Hospital—CHU Charleroi, 6032 Charleroi, Belgium
| | - Marga Buzatu
- Pediatric Neurology, Marie Curie Hospital—CHU Charleroi, 6032 Charleroi, Belgium
| | - Anna Jansen
- Pediatric Neurology Unit, Department of Pediatrics, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Emmanuel Scalais
- Pediatric Neurology Unit, Department of Pediatrics, Centre Hospitalier de Luxembourg, 1313 Luxembourg, Luxembourg
| | - Siddharth Srivastava
- Department of Neurology, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02108, USA
| | - Wen Hann Tan
- Department of Genetics, Boston Children’s Hospital, Boston, MA 02108, USA
| | - Heather E Olson
- Department of Neurology, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02108, USA
- Epilepsy Genetics Program, Boston Children’s Hospital, Boston, MA 02108, USA
| | - Tobias Loddenkemper
- Department of Neurology, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02108, USA
| | - Annapurna Poduri
- Department of Neurology, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02108, USA
- Epilepsy Genetics Program, Boston Children’s Hospital, Boston, MA 02108, USA
| | - Katherine L Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- The Epilepsy Neurogenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Ingo Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- The Epilepsy Neurogenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA 19104 USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
- Institute of Clinical Molecular Biology, Kiel University, 24105 Kiel, Germany
- Department of Neuropediatrics, Kiel University, 24105 Kiel, Germany
| | - Mark P Fitzgerald
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- The Epilepsy Neurogenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA 19104 USA
- Institute of Clinical Molecular Biology, Kiel University, 24105 Kiel, Germany
| | - Ethan M Goldberg
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- The Epilepsy Neurogenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Timo Roser
- Division of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Department of Pediatrics, Dr. von Haunersches Children’s Hospital, Ludwig-Maximilian-University of Munich, 80331 Munich, Germany
| | - Ingo Borggraefe
- Division of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Department of Pediatrics, Dr. von Haunersches Children’s Hospital, Ludwig-Maximilian-University of Munich, 80331 Munich, Germany
- Comprehensive Epilepsy Center, Ludwig-Maximilian- University of Munich, 80331 Munich, Germany
| | - Tobias Brünger
- Luxembourg Centre for Systems Biomedicine (LCSB), University Luxembourg, L-4243 Esch-sur-Alzette, Luxembourg
| | - Patrick May
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44102, USA
| | - Dennis Lal
- Luxembourg Centre for Systems Biomedicine (LCSB), University Luxembourg, L-4243 Esch-sur-Alzette, Luxembourg
- Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH 44102, USA
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and M.I.T., Cambridge, MA 02138, USA
- Cologne Center for Genomics (CCG), University of Cologne, 50667 Cologne, Germany
| | - Damien Lederer
- Institute for Pathology and Genetics, 6040 Gosselies, Belgium
| | - Guido Rubboli
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
- University of Copenhagen, 2200 Copenhagen, Denmark
| | - Henrike O Heyne
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, 4275 Leipzig, Germany
- Finnish Institute for Molecular Medicine (FIMM), University of Helsinki, 320 Helsinki, Finland
- Program for Medical and Population Genetics/Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02138, USA
- Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA 02108, USA
| | - Gaetan Lesca
- Department of Medical Genetics, Groupement Hospitalier Est and ERN EpiCARE, University Hospitals of Lyon (HCL), 69001 Lyon, France
- Institut Neuromyogène, CNRS UMR 5310 - INSERM U1217, Université de Lyon, Université Claude Bernard Lyon 1, 69001 Lyon, France
| | - Ulrike B S Hedrich
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Jan Benda
- Institute for Neurobiology, University of Tuebingen, 72072 Tuebingen, Germany
| | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
- Institute for Regional Health Services, University of Southern Denmark, 5230 Odense, Denmark
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, 72072 Tuebingen, Germany
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Center, 4293 Dianalund, Denmark
- Institute for Regional Health Services, University of Southern Denmark, 5230 Odense, Denmark
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15
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Hammer MF, Pan Y, Cumbay M, Pendziwiat M, Afawi Z, Goldberg-Stern H, Johnstone L, Helbig I, Cummins TR. Whole exome sequencing and co-expression analysis identify an SCN1A variant that modifies pathogenicity in a family with genetic epilepsy and febrile seizures plus. Epilepsia 2022; 63:1970-1980. [PMID: 35592948 PMCID: PMC10753192 DOI: 10.1111/epi.17296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 05/06/2022] [Accepted: 05/06/2022] [Indexed: 01/19/2023]
Abstract
OBJECTIVE Family members carrying the same SCN1A variant often exhibit differences in the clinical severity of epilepsy. This variable expressivity suggests that other factors aside from the primary sodium channel variant influence the clinical manifestation. However, identifying such factors has proven challenging in humans. METHODS We perform whole exome sequencing (WES) in a large family in which an SCN1A variant (p.K1372E) is segregating that is associated with a broad spectrum of phenotypes ranging from lack of epilepsy, to febrile seizures and absence seizures, to Dravet syndrome. We assessed the hypothesis that the severity of the SCN1A-related phenotype was affected by alternate alleles at a modifier locus (or loci). RESULTS One of our top candidates identified by WES was a second variant in the SCN1A gene (p.L375S) that was shared exclusively by unaffected carriers of the K1372E allele. To test the hypothesized that L375S variant nullifies the loss-of-function effect of K1372E, we transiently expressed Nav1.1 carrying the two variants in HEK293T cells and compared their biophysical properties with the wild-type (WT) variant, and then co-expressed WT with K1372E or L375S with K1372E in equal quantity and tested the functional consequence. The data demonstrated that co-expression of the L375S and K1372E alleles reversed the loss-of-function property brought by the K1372E variant, whereas WT-K1372E co-expression remained partial loss-of-function. SIGNIFICANCE These results support the hypothesis that L375S counteracts the loss-of-function effect of K1372E such that individuals carrying both alleles in trans do not present epilepsy-related symptoms. We demonstrate that monogenic epilepsies with wide expressivity can be modified by additional variants in the disease gene, providing a novel framework for the gene-phenotype relationship in genetic epilepsies.
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Affiliation(s)
- Michael F. Hammer
- BIO5 Institute, University of Arizona, Tucson AZ USA
85716
- University of Arizona Genomics Core (UAGC), University of
Arizona, Tucson AZ USA 85716
| | - Yanling Pan
- Department of Biology, Indiana University-Purdue University
Indianapolis, Indianapolis IN 46202
| | - Medhane Cumbay
- Division of Biomedical Sciences, Marian University -
College of Osteopathic Medicine, Indianapolis, IN 46222
| | - Manuela Pendziwiat
- Department of Neuropediatrics, University Medical Center
Schleswig-Holstein Christian Albrechts University, Kiel, Germany
- Institute of Clinical Molecular Biology,
Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Zaid Afawi
- Center for Neuroscience, Ben-Gurion University of the
Negev, Be’er Sheva 8410402, Israel
| | | | - Laurel Johnstone
- University of Arizona Genomics Core (UAGC), University of
Arizona, Tucson AZ USA 85716
| | - Ingo Helbig
- Institute of Clinical Molecular Biology,
Christian-Albrechts-University of Kiel, Kiel, Germany
- Division of Neurology, Children’s Hospital of
Philadelphia, Philadelphia, PA, 19104 USA
- The Epilepsy NeuroGenetics Initiative (ENGIN),
Children’s Hospital of Philadelphia, Philadelphia, USA
- Department of Biomedical and Health Informatics (DBHi),
Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
- Department of Neurology, University of Pennsylvania,
Perelman School of Medicine, Philadelphia, PA, 19104 USA
| | - Theodore R. Cummins
- Department of Biology, Indiana University-Purdue University
Indianapolis, Indianapolis IN 46202
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16
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Zhang P, Zheng P, Ji X, Gao Y, Zhang X, Chen Q. Generation of a human induced pluripotent stem cell line (CIPi002-A) from an early infantile epileptic encephalopathy patient with a heterozygous mutation in SCN8A. Stem Cell Res 2022; 63:102862. [PMID: 35853415 DOI: 10.1016/j.scr.2022.102862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 07/08/2022] [Indexed: 11/17/2022] Open
Abstract
SCN8A is linked to early infantile epileptic encephalopathy type 13 (EIEE13). We generate a human induced pluripotent stem cell (iPSC) line from a child diagnosed with EIEE, caused by SCN8A variation. The iPSC line expresses high pluripotency markers, retains SCN8A variation and is able to differentiate into three germ layers in vitro. The iPSC lines will provide useful resources for studying the pathogenesis and drug screening of SCN8A-related epilepsy.
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Affiliation(s)
- Pingping Zhang
- Department of Neurology, Capital Institute of Pediatrics, China
| | - Ping Zheng
- Department of Neurology, Capital Institute of Pediatrics, China
| | - Xinna Ji
- Department of Neurology, Capital Institute of Pediatrics, China
| | - Yanyan Gao
- Department of Neurology, Capital Institute of Pediatrics, China
| | | | - Qian Chen
- Department of Neurology, Capital Institute of Pediatrics, China.
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17
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Zybura AS, Sahoo FK, Hudmon A, Cummins TR. CaMKII Inhibition Attenuates Distinct Gain-of-Function Effects Produced by Mutant Nav1.6 Channels and Reduces Neuronal Excitability. Cells 2022; 11:2108. [PMID: 35805192 PMCID: PMC9266207 DOI: 10.3390/cells11132108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/16/2022] [Accepted: 06/27/2022] [Indexed: 11/17/2022] Open
Abstract
Aberrant Nav1.6 activity can induce hyperexcitability associated with epilepsy. Gain-of-function mutations in the SCN8A gene encoding Nav1.6 are linked to epilepsy development; however, the molecular mechanisms mediating these changes are remarkably heterogeneous and may involve post-translational regulation of Nav1.6. Because calcium/calmodulin-dependent protein kinase II (CaMKII) is a powerful modulator of Nav1.6 channels, we investigated whether CaMKII modulates disease-linked Nav1.6 mutants. Whole-cell voltage clamp recordings in ND7/23 cells show that CaMKII inhibition of the epilepsy-related mutation R850Q largely recapitulates the effects previously observed for WT Nav1.6. We also characterized a rare missense variant, R639C, located within a regulatory hotspot for CaMKII modulation of Nav1.6. Prediction software algorithms and electrophysiological recordings revealed gain-of-function effects for R639C mutant channel activity, including increased sodium currents and hyperpolarized activation compared to WT Nav1.6. Importantly, the R639C mutation ablates CaMKII phosphorylation at a key regulatory site, T642, and, in contrast to WT and R850Q channels, displays a distinct response to CaMKII inhibition. Computational simulations demonstrate that modeled neurons harboring the R639C or R850Q mutations are hyperexcitable, and simulating the effects of CaMKII inhibition on Nav1.6 activity in modeled neurons differentially reduced hyperexcitability. Acute CaMKII inhibition may represent a promising mechanism to attenuate gain-of-function effects produced by Nav1.6 mutations.
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Affiliation(s)
- Agnes S. Zybura
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
| | - Firoj K. Sahoo
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (F.K.S.); (A.H.)
| | - Andy Hudmon
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (F.K.S.); (A.H.)
| | - Theodore R. Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Biology Department, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
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18
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Xiao Y, Theile JW, Zybura A, Pan Y, Lin Z, Cummins TR. A-type FHFs mediate resurgent currents through TTX-resistant voltage-gated sodium channels. eLife 2022; 11:77558. [PMID: 35441593 PMCID: PMC9071269 DOI: 10.7554/elife.77558] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
Resurgent currents (INaR) produced by voltage-gated sodium channels are required for many neurons to maintain high-frequency firing, and contribute to neuronal hyperexcitability and disease pathophysiology. Here we show, for the first time, that INaR can be reconstituted in a heterologous system by co-expression of sodium channel α-subunits and A-type fibroblast growth factor homologous factors (FHFs). Specifically, A-type FHFs induces INaR from Nav1.8, Nav1.9 tetrodotoxin-resistant neuronal channels and, to a lesser extent, neuronal Nav1.7 and cardiac Nav1.5 channels. Moreover, we identified the N-terminus of FHF as the critical molecule responsible for A-type FHFs-mediated INaR. Among the FHFs, FHF4A is the most important isoform for mediating Nav1.8 and Nav1.9 INaR. In nociceptive sensory neurons, FHF4A knockdown significantly reduces INaR amplitude and the percentage of neurons that generate INaR, substantially suppressing excitability. Thus, our work reveals a novel molecular mechanism underlying TTX-resistant INaR generation and provides important potential targets for pain treatment.
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Affiliation(s)
- Yucheng Xiao
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
| | | | - Agnes Zybura
- Paul and Carole Stark Neurosciences Research Institute, Indiana University, Indianapolis, United States
| | - Yanling Pan
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
| | | | - Theodore R Cummins
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
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19
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Johnson JP, Focken T, Khakh K, Tari PK, Dube C, Goodchild SJ, Andrez JC, Bankar G, Bogucki D, Burford K, Chang E, Chowdhury S, Dean R, de Boer G, Decker S, Dehnhardt C, Feng M, Gong W, Grimwood M, Hasan A, Hussainkhel A, Jia Q, Lee S, Li J, Lin S, Lindgren A, Lofstrand V, Mezeyova J, Namdari R, Nelkenbrecher K, Shuart NG, Sojo L, Sun S, Taron M, Waldbrook M, Weeratunge D, Wesolowski S, Williams A, Wilson M, Xie Z, Yoo R, Young C, Zenova A, Zhang W, Cutts AJ, Sherrington RP, Pimstone SN, Winquist R, Cohen CJ, Empfield JR. NBI-921352, a first-in-class, Na V1.6 selective, sodium channel inhibitor that prevents seizures in Scn8a gain-of-function mice, and wild-type mice and rats. eLife 2022; 11:72468. [PMID: 35234610 PMCID: PMC8903829 DOI: 10.7554/elife.72468] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 02/23/2022] [Indexed: 11/21/2022] Open
Abstract
NBI-921352 (formerly XEN901) is a novel sodium channel inhibitor designed to specifically target NaV1.6 channels. Such a molecule provides a precision-medicine approach to target SCN8A-related epilepsy syndromes (SCN8A-RES), where gain-of-function (GoF) mutations lead to excess NaV1.6 sodium current, or other indications where NaV1.6 mediated hyper-excitability contributes to disease (Gardella and Møller, 2019; Johannesen et al., 2019; Veeramah et al., 2012). NBI-921352 is a potent inhibitor of NaV1.6 (IC500.051 µM), with exquisite selectivity over other sodium channel isoforms (selectivity ratios of 756 X for NaV1.1, 134 X for NaV1.2, 276 X for NaV1.7, and >583 Xfor NaV1.3, NaV1.4, and NaV1.5). NBI-921352is a state-dependent inhibitor, preferentially inhibiting inactivatedchannels. The state dependence leads to potent stabilization of inactivation, inhibiting NaV1.6 currents, including resurgent and persistent NaV1.6 currents, while sparing the closed/rested channels. The isoform-selective profile of NBI-921352 led to a robust inhibition of action-potential firing in glutamatergic excitatory pyramidal neurons, while sparing fast-spiking inhibitory interneurons, where NaV1.1 predominates. Oral administration of NBI-921352 prevented electrically induced seizures in a Scn8a GoF mouse,as well as in wild-type mouse and ratseizure models. NBI-921352 was effective in preventing seizures at lower brain and plasma concentrations than commonly prescribed sodium channel inhibitor anti-seizure medicines (ASMs) carbamazepine, phenytoin, and lacosamide. NBI-921352 waswell tolerated at higher multiples of the effective plasma and brain concentrations than those ASMs. NBI-921352 is entering phase II proof-of-concept trials for the treatment of SCN8A-developmental epileptic encephalopathy (SCN8A-DEE) and adult focal-onset seizures.
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Affiliation(s)
- J P Johnson
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Thilo Focken
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Kuldip Khakh
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Celine Dube
- In Vivo Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | | | - Girish Bankar
- In Vivo Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - David Bogucki
- Chemistry, Medipure Pharmaceuticals, Burnaby BC, Canada
| | | | - Elaine Chang
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Richard Dean
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Gina de Boer
- Compound Properties, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Shannon Decker
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Mandy Feng
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Wei Gong
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Abid Hasan
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Qi Jia
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Stephanie Lee
- Compound Properties, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Jenny Li
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Sophia Lin
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Andrea Lindgren
- Compound Properties, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Janette Mezeyova
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Rostam Namdari
- Translational Drug Development, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | | | - Luis Sojo
- Compound Properties, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Shaoyi Sun
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Matthew Taron
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Diana Weeratunge
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | - Aaron Williams
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Michael Wilson
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Zhiwei Xie
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Rhena Yoo
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Clint Young
- In Vitro Biology, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Alla Zenova
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Wei Zhang
- Chemistry, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | - Alison J Cutts
- Scientific Affairs, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
| | | | | | | | - Charles J Cohen
- Executive Team, Xenon Pharmaceuticals, Inc., Burnaby BC, Canada
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20
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Shapiro L, Escayg A, Wong JC. Cannabidiol Increases Seizure Resistance and Improves Behavior in an Scn8a Mouse Model. Front Pharmacol 2022; 13:815950. [PMID: 35153788 PMCID: PMC8826257 DOI: 10.3389/fphar.2022.815950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/04/2022] [Indexed: 12/11/2022] Open
Abstract
Voltage-gated sodium channel genes are an important family of human epilepsy genes. De novo missense mutations in SCN8A (encoding Nav1.6) are associated with a spectrum of clinical presentation, including multiple seizure types, movement disorders, intellectual disability, and behavioral abnormalities such as autism. Patients with SCN8A mutations are often treated with multiple antiepileptic drugs, the most common being sodium channel blockers. Cannabidiol (CBD) has been included as a component of treatment regimens for some SCN8A patients; however, to date, there are no clinical trials that have evaluated the therapeutic potential of CBD in patients with SCN8A mutations. In the current manuscript, we demonstrated a dose-dependent increase in seizure resistance following CBD treatment in mice expressing the human SCN8A mutation R1620L (RL/+). We also found that CBD treatment improved social behavior and reduced hyperactivity in the RL/+ mutants. Our findings suggest that CBD may be beneficial in patients with SCN8A-associated disease.
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Affiliation(s)
- Lindsey Shapiro
- Department of Human Genetics, Emory University, Atlanta, GA, United States
| | - Andrew Escayg
- Department of Human Genetics, Emory University, Atlanta, GA, United States
| | - Jennifer C Wong
- Department of Human Genetics, Emory University, Atlanta, GA, United States
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21
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Liu Y, Koko M, Lerche H. A SCN8A variant associated with severe early onset epilepsy and developmental delay: Loss- or gain-of-function? Epilepsy Res 2021; 178:106824. [PMID: 34847423 DOI: 10.1016/j.eplepsyres.2021.106824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/12/2021] [Accepted: 11/16/2021] [Indexed: 10/19/2022]
Abstract
SCN8A, encoding the voltage-gated sodium channel subunit NaV1.6, has been associated with a wide spectrum of neuropsychiatric disorders. Missense variants in SCN8A which increase the channel activity can cause a severe developmental and epileptic encephalopathy (DEE). One DEE variant (p.(Arg223Gly)) was described to cause a predominant loss-of-function (LOF) mechanism when expressed in neuroblastoma cells, which is not consistent with the genotype-phenotype correlations in this gene. To resolve this discrepancy and understand the pathophysiological mechanism of this variant, we performed comprehensive electrophysiological studies in both neuroblastoma cells and primary hippocampal neuronal cultures. Although we also found that p.(Arg223Gly) significantly decreased Na+ current density and enhanced fast inactivation compared to the wild type (WT) channel in transfected neuroblastoma cells (both LOF mechanisms), it also caused a strong hyperpolarizing shift of steady-state activation and accelerated the recovery from fast inactivation (both gain-of-function (GOF) mechanisms). In cultured neurons transfected with mutant vs. WT NaV1.6 channels, we found more depolarized resting membrane potentials and a decreased rheobase leading to enhanced action potential firing. We conclude that SCN8A p.(Arg223Gly) leads to a net GOF resulting in neuronal hyperexcitability and a higher firing rate, fitting with the central role of GOF mechanisms in DEE.
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Affiliation(s)
- Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Mahmoud Koko
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany.
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22
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Quattrocolo G, Dunville K, Nigro MJ. Resurgent Sodium Current in Neurons of the Cerebral Cortex. Front Cell Neurosci 2021; 15:760610. [PMID: 34658797 PMCID: PMC8517112 DOI: 10.3389/fncel.2021.760610] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 09/13/2021] [Indexed: 11/29/2022] Open
Abstract
In the late ’90, Dr. Indira Raman, at the time a postdoctoral fellow with Dr. Bruce Bean, at Harvard University, identified a new type of sodium current, flowing through the channels that reopens when the membrane is repolarized. This current, called “resurgent Sodium current,” was originally identified in cerebellar Purkinje neurons and has now been confirmed in around 20 different neuronal types. Since moving to Northwestern University in 1999 to establish her own research group, Dr. Raman has dedicated great efforts in identifying the mechanisms supporting the resurgent Sodium current and how its biophysical properties shape the firing of the different cell types. Her work has impacted greatly the field of cellular neurophysiology, from basic research to translation neuroscience. In fact, alterations in the resurgent sodium currents have been observed in several neuropathologies, from Huntington’s disease to epilepsy. In this Perspective we will focus on the current knowledge on the expression and function of the resurgent Sodium current in neurons of the cerebral cortex and hippocampus. We will also briefly highlight the role of Dr. Raman’s as teacher and mentor, not only for her pupils, but for the whole scientific community.
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Affiliation(s)
- Giulia Quattrocolo
- Center for Neural Computation, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
| | - Keagan Dunville
- Center for Neural Computation, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
| | - Maximiliano José Nigro
- Center for Neural Computation, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
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23
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Zybura A, Hudmon A, Cummins TR. Distinctive Properties and Powerful Neuromodulation of Na v1.6 Sodium Channels Regulates Neuronal Excitability. Cells 2021; 10:cells10071595. [PMID: 34202119 PMCID: PMC8307729 DOI: 10.3390/cells10071595] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/20/2021] [Accepted: 06/21/2021] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (Navs) are critical determinants of cellular excitability. These ion channels exist as large heteromultimeric structures and their activity is tightly controlled. In neurons, the isoform Nav1.6 is highly enriched at the axon initial segment and nodes, making it critical for the initiation and propagation of neuronal impulses. Changes in Nav1.6 expression and function profoundly impact the input-output properties of neurons in normal and pathological conditions. While mutations in Nav1.6 may cause channel dysfunction, aberrant changes may also be the result of complex modes of regulation, including various protein-protein interactions and post-translational modifications, which can alter membrane excitability and neuronal firing properties. Despite decades of research, the complexities of Nav1.6 modulation in health and disease are still being determined. While some modulatory mechanisms have similar effects on other Nav isoforms, others are isoform-specific. Additionally, considerable progress has been made toward understanding how individual protein interactions and/or modifications affect Nav1.6 function. However, there is still more to be learned about how these different modes of modulation interact. Here, we examine the role of Nav1.6 in neuronal function and provide a thorough review of this channel’s complex regulatory mechanisms and how they may contribute to neuromodulation.
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Affiliation(s)
- Agnes Zybura
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Biology Department, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Andy Hudmon
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA;
| | - Theodore R. Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Biology Department, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
- Correspondence:
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24
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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] [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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25
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Praticò A, Gulizia C, Gangi G, Oliva C, Romano C, Marino S, Polizzi A, Ruggieri M, Falsaperla R. SCN8A and Its Related Epileptic Phenotypes. JOURNAL OF PEDIATRIC NEUROLOGY 2021. [DOI: 10.1055/s-0041-1729142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractSodium channelopathies are among the most common single-gene causes of epilepsy and have been considered model disorders for the study of genetic epilepsies. Epilepsies due to SCN8A pathogenic variants can present with a broad range of phenotypes varying from a severe epileptic encephalopathy with multiple types of drug-resistant seizure to neurodevelopmental delay, mental retardation, and electroencephalogram (EEG) findings of multifocal spike and waves (mostly in the temporal/parietal/occipital areas). In rare cases, benign familial infantile seizures and developmental delay with/without ataxia have been reported. A first-level, specific SCN8A Sanger's sequencing, although available, is rarely performed because the clinical phenotype is not strictly characteristic and several overlaps with other genetic epilepsies may occur. Given its indistinctive phenotype, diagnosis is usually performed through a specific gene panel for epileptic encephalopathies, early epilepsies, or genetic epilepsy in general, or through whole exome sequencing (WES) and more rarely through whole genome sequencing (WGS). Mutations in SCN8A occur as an autosomal dominant trait. The great majority of individuals diagnosed with SCN8A epilepsy do not have an affected parent, because usually SCN8A patients do not reproduce, and mutations are inherited as a “de novo” trait. In rare cases, SCN8A mutations may be inherited in the setting of parental germline mosaicism. SCN8A-related epilepsies have not shown a clear genotype–phenotype correlation, the same variants have been described with different clinical expressivity and this could be due to other genetic factors or to interacting environmental factors. There is no standardized treatment for SCN8A-related epilepsy because of the rarity of the disease and the unavailability of specific, targeted drugs. Treatment is based mainly on antiepileptic drugs which include classic wide-spectrum drugs such as valproic acid, levetiracetam, and lamotrigine. Sodium-channel blockers (phenytoin, carbamazepine, oxcarbazepine, and lamotrigine) have shown appreciable results in terms of seizure reduction, in particular, in patients presenting gain-of-function mutations. Nowadays, new potentially transformative gene therapy treatment approaches are currently being explored, allowing in the next future, a precision-based treatment directed against the gene defect and protein alterations.
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Affiliation(s)
- Andrea Praticò
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, Catania, Italy
| | - Carmela Gulizia
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Gloria Gangi
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Claudia Oliva
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | | | - Simona Marino
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Agata Polizzi
- Chair of Pediatrics, Department of Educational Sciences, University of Catania, Catania, Italy
| | - Martino Ruggieri
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, Catania, Italy
| | - Raffaele Falsaperla
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
- Chair of Pediatrics, Department of Educational Sciences, University of Catania, Catania, Italy
- Unit of Neonatal Intensive Care and Neonatology, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
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26
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Mantegazza M, Cestèle S, Catterall WA. Sodium channelopathies of skeletal muscle and brain. Physiol Rev 2021; 101:1633-1689. [PMID: 33769100 DOI: 10.1152/physrev.00025.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Voltage-gated sodium channels initiate action potentials in nerve, skeletal muscle, and other electrically excitable cells. Mutations in them cause a wide range of diseases. These channelopathy mutations affect every aspect of sodium channel function, including voltage sensing, voltage-dependent activation, ion conductance, fast and slow inactivation, and both biosynthesis and assembly. Mutations that cause different forms of periodic paralysis in skeletal muscle were discovered first and have provided a template for understanding structure, function, and pathophysiology at the molecular level. More recent work has revealed multiple sodium channelopathies in the brain. Here we review the well-characterized genetics and pathophysiology of the periodic paralyses of skeletal muscle and then use this information as a foundation for advancing our understanding of mutations in the structurally homologous α-subunits of brain sodium channels that cause epilepsy, migraine, autism, and related comorbidities. We include studies based on molecular and structural biology, cell biology and physiology, pharmacology, and mouse genetics. Our review reveals unexpected connections among these different types of sodium channelopathies.
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Affiliation(s)
- Massimo Mantegazza
- Université Cote d'Azur, Valbonne-Sophia Antipolis, France.,CNRS UMR7275, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne-Sophia Antipolis, France.,INSERM, Valbonne-Sophia Antipolis, France
| | - Sandrine Cestèle
- Université Cote d'Azur, Valbonne-Sophia Antipolis, France.,CNRS UMR7275, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne-Sophia Antipolis, France
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27
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Ademuwagun IA, Rotimi SO, Syrbe S, Ajamma YU, Adebiyi E. Voltage Gated Sodium Channel Genes in Epilepsy: Mutations, Functional Studies, and Treatment Dimensions. Front Neurol 2021; 12:600050. [PMID: 33841294 PMCID: PMC8024648 DOI: 10.3389/fneur.2021.600050] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 03/01/2021] [Indexed: 12/19/2022] Open
Abstract
Genetic epilepsy occurs as a result of mutations in either a single gene or an interplay of different genes. These mutations have been detected in ion channel and non-ion channel genes. A noteworthy class of ion channel genes are the voltage gated sodium channels (VGSCs) that play key roles in the depolarization phase of action potentials in neurons. Of huge significance are SCN1A, SCN1B, SCN2A, SCN3A, and SCN8A genes that are highly expressed in the brain. Genomic studies have revealed inherited and de novo mutations in sodium channels that are linked to different forms of epilepsies. Due to the high frequency of sodium channel mutations in epilepsy, this review discusses the pathogenic mutations in the sodium channel genes that lead to epilepsy. In addition, it explores the functional studies on some known mutations and the clinical significance of VGSC mutations in the medical management of epilepsy. The understanding of these channel mutations may serve as a strong guide in making effective treatment decisions in patient management.
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Affiliation(s)
- Ibitayo Abigail Ademuwagun
- Covenant University Bioinformatics Research, Covenant University, Ota, Nigeria
- Department of Biochemistry, Covenant University, Ota, Nigeria
| | - Solomon Oladapo Rotimi
- Covenant University Bioinformatics Research, Covenant University, Ota, Nigeria
- Department of Biochemistry, Covenant University, Ota, Nigeria
| | - Steffen Syrbe
- Clinic for Pediatric and Adolescent Medicine, Heidelberg University, Heidelberg, Germany
| | | | - Ezekiel Adebiyi
- Covenant University Bioinformatics Research, Covenant University, Ota, Nigeria
- Department of Computer and Information Sciences, Covenant University, Ota, Nigeria
- Division of Applied Bioinformatics, German Cancer Research Center (DKFZ), Heidelberg, Germany
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28
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Abstract
The voltage-gated sodium channel α-subunit genes comprise a highly conserved gene family. Mutations of three of these genes, SCN1A, SCN2A and SCN8A, are responsible for a significant burden of neurological disease. Recent progress in identification and functional characterization of patient variants is generating new insights and novel approaches to therapy for these devastating disorders. Here we review the basic elements of sodium channel function that are used to characterize patient variants. We summarize a large body of work using global and conditional mouse mutants to characterize the in vivo roles of these channels. We provide an overview of the neurological disorders associated with mutations of the human genes and examples of the effects of patient mutations on channel function. Finally, we highlight therapeutic interventions that are emerging from new insights into mechanisms of sodium channelopathies.
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29
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Poulin H, Chahine M. R1617Q epilepsy mutation slows Na V 1.6 sodium channel inactivation and increases the persistent current and neuronal firing. J Physiol 2021; 599:1651-1664. [PMID: 33442870 DOI: 10.1113/jp280838] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/21/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS A human NaV 1.6 construct was established to study the biophysical consequences of the R1617Q mutation on NaV 1.6 identified in patients with unclassified epileptic encephalopathy and severe intellectual disability. The R1617Q mutation disrupts the inactivation process of the channel, and more specifically, slows the current decay, increases the persistent sodium current that was blocked by tetrodotoxin and riluzole, and disrupts the inactivation voltage-dependence and increases the kinetics of recovery. In native hippocampal neurons, the R1617Q mutation exhibited a significant increase in action potentials triggered in response to stimulation and a significant increase in the number of neurons that exhibited spontaneous activity compared to neurons expressing WT channels that were inhibited by riluzole. The abnormally persistent current activity caused by the disruption of the channel inactivation process in NaV 1.6/R1617Q may result in epileptic encephalopathy in patients. ABSTRACT The voltage-gated sodium channel NaV 1.6 is the most abundantly expressed sodium channel isoform in the central nervous system. It plays a critical role in saltatory and continuous conduction. Although over 40 NaV 1.6 mutations have been linked to epileptic encephalopathy, only a few have been functionally analysed. In the present study, we characterized a NaV 1.6 mutation (R1617Q) identified in patients with epileptic encephalopathy and intellectual disability. R1617Q substitutes an arginine for a glutamine in the S4 segment of domain IV, which plays a major role in coupling the activation and inactivation of sodium channels. We used patch-clamp to show that R1617Q is a gain-of-function mutation. It is typified by slower inactivation kinetics and a loss of inactivation of voltage-dependence, which result in a 2.5-fold increase in the window current. In addition, sodium currents exhibited an enhanced rate of recovery from inactivation, most likely due to the destabilization of the inactivation state. The alterations in the fast inactivation caused a significant increase in the persistent sodium current. Overexpression of R1617Q in rat hippocampal neurons resulted in an increase in action potential firing activity that was inhibited by riluzole, consistent with the gain-of-function observed. We conclude that the R1617Q mutation causes neuronal hyperexcitability and may result in epileptic encephalopathy.
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Affiliation(s)
- Hugo Poulin
- CERVO Brain Research Centre, Quebec City, Québec, Canada
| | - Mohamed Chahine
- CERVO Brain Research Centre, Quebec City, Québec, Canada.,Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada
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30
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Abstract
Voltage-gated sodium channels (VGSCs) are foundational to excitable cell function: Their coordinated passage of sodium ions into the cell is critical for the generation and propagation of action potentials throughout the nervous system. The classical paradigm of action potential physiology states that sodium passes through the membrane only transiently (1-2 milliseconds), before the channels inactivate and cease to conduct sodium ions. However, in reality, a small fraction of the total sodium current (1%-2%) remains at steady state despite prolonged depolarization. While this persistent sodium current (INaP) contributes to normal physiological functioning of neurons, accumulating evidence indicates a particularly pathogenic role for an elevated INaP in epilepsy (reviewed previously1). Due to significant advances over the past decade of epilepsy research concerning the importance of INaP in sodium channelopathies, this review seeks to summarize recent evidence and highlight promising novel anti-seizure medication strategies through preferentially targeting INaP.
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Affiliation(s)
- Eric R. Wengert
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
| | - Manoj K. Patel
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA, USA
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31
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Inhibitory Effectiveness of Gomisin A, a Dibenzocyclooctadiene Lignan Isolated from Schizandra chinensis, on the Amplitude and Gating of Voltage-Gated Na + Current. Int J Mol Sci 2020; 21:ijms21228816. [PMID: 33233411 PMCID: PMC7700137 DOI: 10.3390/ijms21228816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 11/18/2020] [Accepted: 11/19/2020] [Indexed: 12/12/2022] Open
Abstract
Gomisin A (Gom A), a lignan isolated from Schisandra chinensis, has been reported produce numerous biological activities. However, its action on the ionic mechanisms remains largely unanswered. The present experiments were undertaken to investigate the possible perturbations of Gom A or other related compounds on different types of membrane ionic currents in electrically excitable cells (i.e., pituitary GH3 and pancreatic INS-1 cells). The exposure to Gom A led to the differential inhibition of peak and end-pulse components of voltage-gated Na+ current (INa) in GH3 cells with effective IC50 of 6.2 and 0.73 μM, respectively. The steady-state inactivation curve of INa in the presence of Gom A was shifted towards a more hyperpolarized potential. However, neither changes in the overall current-voltage relationship nor those for the gating charge of the current were demonstrated. The application of neither morin (10 μM) nor hesperidin (10 μM) perturbed the strength of INa, while sesamine could suppress it. However, in the continued presence of Gom A, the addition of sesamine failed to suppress INa further. Gom A also effectively suppressed the strength of persistent INa activated by long ramp voltage command, and further application of tefluthrin effectively attenuated Gom A-mediated inhibition of the current. The presence of Gom A mildly inhibited erg-mediated K+ current, while a lack of change in the amplitude of hyperpolarization-activated cation current was observed in its presence. Under cell-attached current recordings, the exposure to Gom A resulted in the decreased firing of spontaneous action currents with a minimal change in AC amplitude. In pancreatic INS-1 cells, the presence of Gom A was also noticed to inhibit peak and end-pulse components of INa differentially with the IC50 of 5.9 and 0.84 μM, respectively. Taken together, the emerging results presented herein provide the evidence that Gom A can differentially inhibit peak and sustained INa in endocrine cells (e.g., GH3 and INS-1 cells).
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32
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Solé L, Wagnon JL, Tamkun MM. Functional analysis of three Na v1.6 mutations causing early infantile epileptic encephalopathy. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165959. [PMID: 32916281 DOI: 10.1016/j.bbadis.2020.165959] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 08/21/2020] [Accepted: 09/03/2020] [Indexed: 11/24/2022]
Abstract
The voltage-gated sodium channel Nav1.6 is associated with more than 300 cases of epileptic encephalopathy. Nav1.6 epilepsy-causing mutations are spread over the entire channel's structure and only 10% of mutations have been characterized at the molecular level, with most of them being gain of function mutations. In this study, we analyzed three previously uncharacterized Nav1.6 epilepsy-causing mutations: G214D, N215D and V216D, located within a mutation hot-spot at the S3-S4 extracellular loop of Domain1. Voltage clamp experiments showed a 6-16 mV hyperpolarizing shift in the activation mid-point for all three mutants. V216D presented the largest shift along with decreased current amplitude, enhanced inactivation and a lack of persistent current. Recordings at hyperpolarized potentials indicated that all three mutants presented gating pore currents. Furthermore, trafficking experiments performed in cultured hippocampal neurons demonstrated that the mutants trafficked properly to the cell surface, with no significant differences regarding surface expression within the axon initial segment or soma compared to wild-type. These trafficking data suggest that the disease-causing consequences are due to only changes in the biophysical properties of the channel. Interestingly, the patient carrying the V216D mutation, which is the mutant with the greatest electrophysiological changes as compared to wild-type, exhibited the most severe phenotype. These results emphasize that these mutations will mandate unique treatment approaches, for normal sodium channel blockers may not work given that the studied mutations present gating pore currents. This study emphasizes the importance of molecular characterization of disease-causing mutations in order to improve the pharmacological treatment of patients.
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Affiliation(s)
- Laura Solé
- Molecular, Cellular and Integrative Neurosciences Graduate Program, Colorado State University, Fort Collins, CO 80523, USA; Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Jacy L Wagnon
- Department of Neuroscience, Wexner Medical Center, The Ohio State University, Columbus, OH 43210, USA
| | - Michael M Tamkun
- Molecular, Cellular and Integrative Neurosciences Graduate Program, Colorado State University, Fort Collins, CO 80523, USA; Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA; Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
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33
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Menezes LFS, Sabiá Júnior EF, Tibery DV, Carneiro LDA, Schwartz EF. Epilepsy-Related Voltage-Gated Sodium Channelopathies: A Review. Front Pharmacol 2020; 11:1276. [PMID: 33013363 PMCID: PMC7461817 DOI: 10.3389/fphar.2020.01276] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 07/31/2020] [Indexed: 12/29/2022] Open
Abstract
Epilepsy is a disease characterized by abnormal brain activity and a predisposition to generate epileptic seizures, leading to neurobiological, cognitive, psychological, social, and economic impacts for the patient. There are several known causes for epilepsy; one of them is the malfunction of ion channels, resulting from mutations. Voltage-gated sodium channels (NaV) play an essential role in the generation and propagation of action potential, and malfunction caused by mutations can induce irregular neuronal activity. That said, several genetic variations in NaV channels have been described and associated with epilepsy. These mutations can affect channel kinetics, modifying channel activation, inactivation, recovery from inactivation, and/or the current window. Among the NaV subtypes related to epilepsy, NaV1.1 is doubtless the most relevant, with more than 1500 mutations described. Truncation and missense mutations are the most observed alterations. In addition, several studies have already related mutated NaV channels with the electrophysiological functioning of the channel, aiming to correlate with the epilepsy phenotype. The present review provides an overview of studies on epilepsy-associated mutated human NaV1.1, NaV1.2, NaV1.3, NaV1.6, and NaV1.7.
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Affiliation(s)
- Luis Felipe Santos Menezes
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Elias Ferreira Sabiá Júnior
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Diogo Vieira Tibery
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Lilian Dos Anjos Carneiro
- Faculdade de Medicina, Centro Universitário Euro Americano, Brasília, Brazil.,Faculdade de Medicina, Centro Universitário do Planalto Central, Brasília, Brazil
| | - Elisabeth Ferroni Schwartz
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
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34
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Adney SK, Millichap JJ, DeKeyser JM, Abramova T, Thompson CH, George AL. Functional and pharmacological evaluation of a novel SCN2A variant linked to early-onset epilepsy. Ann Clin Transl Neurol 2020; 7:1488-1501. [PMID: 32750235 PMCID: PMC7480906 DOI: 10.1002/acn3.51105] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/26/2020] [Accepted: 05/28/2020] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE We identified a novel de novo SCN2A variant (M1879T) associated with infantile-onset epilepsy that responded dramatically to sodium channel blocker antiepileptic drugs. We analyzed the functional and pharmacological consequences of this variant to establish pathogenicity, and to correlate genotype with phenotype and clinical drug response. METHODS The clinical and genetic features of an infant boy with epilepsy are presented. We investigated the effect of the variant using heterologously expressed recombinant human NaV 1.2 channels. We performed whole-cell patch clamp recording to determine the functional consequences and response to carbamazepine. RESULTS The M1879T variant caused disturbances in channel inactivation including substantially depolarized voltage dependence of inactivation, slower time course of inactivation, and enhanced resurgent current that collectively represent a gain-of-function. Carbamazepine partially normalized the voltage dependence of inactivation and produced use-dependent block of the variant channel at high pulsing frequencies. Carbamazepine also suppresses resurgent current conducted by M1879T channels, but this effect was explained primarily by reducing the peak transient current. Molecular modeling suggests that the M1879T variant disrupts contacts with nearby residues in the C-terminal domain of the channel. INTERPRETATION Our study demonstrates the value of conducting functional analyses of SCN2A variants of unknown significance to establish pathogenicity and genotype-phenotype correlations. We also show concordance of in vitro pharmacology using heterologous cells with the drug response observed clinically in a case of SCN2A-associated epilepsy.
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Affiliation(s)
- Scott K Adney
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA
| | - John J Millichap
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA.,Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, 60611, USA
| | - Jean-Marc DeKeyser
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Tatiana Abramova
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Christopher H Thompson
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Alfred L George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
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Kuo PC, Kao ZH, Lee SW, Wu SN. Effects of Sesamin, the Major Furofuran Lignan of Sesame Oil, on the Amplitude and Gating of Voltage-Gated Na + and K + Currents. Molecules 2020; 25:molecules25133062. [PMID: 32635522 PMCID: PMC7411736 DOI: 10.3390/molecules25133062] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/01/2020] [Accepted: 07/01/2020] [Indexed: 12/17/2022] Open
Abstract
Sesamin (SSM) and sesamolin (SesA) are the two major furofuran lignans of sesame oil and they have been previously noticed to exert various biological actions. However, their modulatory actions on different types of ionic currents in electrically excitable cells remain largely unresolved. The present experiments were undertaken to explore the possible perturbations of SSM and SesA on different types of ionic currents, e.g., voltage-gated Na+ currents (INa), erg-mediated K+ currents (IK(erg)), M-type K+ currents (IK(M)), delayed-rectifier K+ currents (IK(DR)) and hyperpolarization-activated cation currents (Ih) identified from pituitary tumor (GH3) cells. The exposure to SSM or SesA depressed the transient and late components of INa with different potencies. The IC50 value of SSM needed to lessen the peak or sustained INa was calculated to be 7.2 or 0.6 μM, while that of SesA was 9.8 or 2.5 μM, respectively. The dissociation constant of SSM-perturbed inhibition on INa, based on the first-order reaction scheme, was measured to be 0.93 μM, a value very similar to the IC50 for its depressant action on sustained INa. The addition of SSM was also effective at suppressing the amplitude of resurgent INa. The addition of SSM could concentration-dependently inhibit the IK(M) amplitude with an IC50 value of 4.8 μM. SSM at a concentration of 30 μM could suppress the amplitude of IK(erg), while at 10 μM, it mildly decreased the IK(DR) amplitude. However, the addition of neither SSM (10 μM) nor SesA (10 μM) altered the amplitude or kinetics of Ih in response to long-lasting hyperpolarization. Additionally, in this study, a modified Markovian model designed for SCN8A-encoded (or NaV1.6) channels was implemented to evaluate the plausible modifications of SSM on the gating kinetics of NaV channels. The model demonstrated herein was well suited to predict that the SSM-mediated decrease in peak INa, followed by increased current inactivation, which could largely account for its favorable decrease in the probability of the open-blocked over open state of NaV channels. Collectively, our study provides evidence that highlights the notion that SSM or SesA could block multiple ion currents, such as INa and IK(M), and suggests that these actions are potentially important and may participate in the functional activities of various electrically excitable cells in vivo.
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Affiliation(s)
- Ping-Chung Kuo
- School of Pharmacy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
| | - Zi-Han Kao
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (Z.-H.K.); (S.-W.L.)
| | - Shih-Wei Lee
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (Z.-H.K.); (S.-W.L.)
| | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (Z.-H.K.); (S.-W.L.)
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan
- Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 40402, Taiwan
- Correspondence: ; Tel.: +886-6-235-3535-5334; Fax: +886-6-2362780
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Singh AK, Wadsworth PA, Tapia CM, Aceto G, Ali SR, Chen H, D'Ascenzo M, Zhou J, Laezza F. Mapping of the FGF14:Nav1.6 complex interface reveals FLPK as a functionally active peptide modulating excitability. Physiol Rep 2020; 8:e14505. [PMID: 32671946 PMCID: PMC7363588 DOI: 10.14814/phy2.14505] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 02/07/2023] Open
Abstract
The voltage-gated sodium (Nav) channel complex is comprised of pore-forming α subunits (Nav1.1-1.9) and accessory regulatory proteins such as the intracellular fibroblast growth factor 14 (FGF14). The cytosolic Nav1.6 C-terminal tail binds directly to FGF14 and this interaction modifies Nav1.6-mediated currents with effects on intrinsic excitability in the brain. Previous studies have identified the FGF14V160 residue within the FGF14 core domain as a hotspot for the FGF14:Nav1.6 complex formation. Here, we used three short amino acid peptides around FGF14V160 to probe for the FGF14 interaction with the Nav1.6 C-terminal tail and to evaluate the activity of the peptide on Nav1.6-mediated currents. In silico docking predicts FLPK to bind to FGF14V160 with the expectation of interfering with the FGF14:Nav1.6 complex formation, a phenotype that was confirmed by the split-luciferase assay (LCA) and surface plasmon resonance (SPR), respectively. Whole-cell patch-clamp electrophysiology studies demonstrate that FLPK is able to prevent previously reported FGF14-dependent phenotypes of Nav1.6 currents, but that its activity requires the FGF14 N-terminal tail, a domain that has been shown to contribute to Nav1.6 inactivation independently from the FGF14 core domain. In medium spiny neurons in the nucleus accumbens, where both FGF14 and Nav1.6 are abundantly expressed, FLPK significantly increased firing frequency by a mechanism consistent with the ability of the tetrapeptide to interfere with Nav1.6 inactivation and potentiate persistent Na+ currents. Taken together, these results indicate that FLPK might serve as a probe for characterizing molecular determinants of neuronal excitability and a peptide scaffold to develop allosteric modulators of Nav channels.
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Affiliation(s)
- Aditya K. Singh
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
| | - Paul A. Wadsworth
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
- M.D.‐Ph.D. Combined Degree ProgramUniversità Cattolica del Sacro CuoreRomeItaly
- Biochemistry and Molecular Biology Graduate ProgramUniversità Cattolica del Sacro CuoreRomeItaly
| | - Cynthia M. Tapia
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
- NIEHS Environmental Toxicology Training ProgramUniversità Cattolica del Sacro CuoreRomeItaly
| | - Giuseppe Aceto
- Institute of Human PhysiologyUniversità Cattolica del Sacro CuoreRomeItaly
- Department of NeuroscienceUniversità Cattolica del Sacro CuoreRomeItaly
- Fondazione Policlinico Universitario A. GemelliIRCCSRomeItaly
| | - Syed R. Ali
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
| | - Haiying Chen
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
| | - Marcello D'Ascenzo
- Institute of Human PhysiologyUniversità Cattolica del Sacro CuoreRomeItaly
- Department of NeuroscienceUniversità Cattolica del Sacro CuoreRomeItaly
- Fondazione Policlinico Universitario A. GemelliIRCCSRomeItaly
| | - Jia Zhou
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
- Center for Addiction ResearchUniversity of Texas Medical BranchGalvestonTXUSA
| | - Fernanda Laezza
- Department of Pharmacology & ToxicologyUniversità Cattolica del Sacro CuoreRomeItaly
- Center for Addiction ResearchUniversity of Texas Medical BranchGalvestonTXUSA
- Center for Neurodegenerative DiseasesUniversity of Texas Medical BranchGalvestonTXUSA
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37
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Zybura AS, Baucum AJ, Rush AM, Cummins TR, Hudmon A. CaMKII enhances voltage-gated sodium channel Nav1.6 activity and neuronal excitability. J Biol Chem 2020; 295:11845-11865. [PMID: 32611770 DOI: 10.1074/jbc.ra120.014062] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/30/2020] [Indexed: 11/06/2022] Open
Abstract
Nav1.6 is the primary voltage-gated sodium channel isoform expressed in mature axon initial segments and nodes, making it critical for initiation and propagation of neuronal impulses. Thus, Nav1.6 modulation and dysfunction may have profound effects on input-output properties of neurons in normal and pathological conditions. Phosphorylation is a powerful and reversible mechanism regulating ion channel function. Because Nav1.6 and the multifunctional Ca2+/CaM-dependent protein kinase II (CaMKII) are independently linked to excitability disorders, we sought to investigate modulation of Nav1.6 function by CaMKII signaling. We show that inhibition of CaMKII, a Ser/Thr protein kinase associated with excitability, synaptic plasticity, and excitability disorders, with the CaMKII-specific peptide inhibitor CN21 reduces transient and persistent currents in Nav1.6-expressing Purkinje neurons by 87%. Using whole-cell voltage clamp of Nav1.6, we show that CaMKII inhibition in ND7/23 and HEK293 cells significantly reduces transient and persistent currents by 72% and produces a 5.8-mV depolarizing shift in the voltage dependence of activation. Immobilized peptide arrays and nanoflow LC-electrospray ionization/MS of Nav1.6 reveal potential sites of CaMKII phosphorylation, specifically Ser-561 and Ser-641/Thr-642 within the first intracellular loop of the channel. Using site-directed mutagenesis to test multiple potential sites of phosphorylation, we show that Ala substitutions of Ser-561 and Ser-641/Thr-642 recapitulate the depolarizing shift in activation and reduction in current density. Computational simulations to model effects of CaMKII inhibition on Nav1.6 function demonstrate dramatic reductions in spontaneous and evoked action potentials in a Purkinje cell model, suggesting that CaMKII modulation of Nav1.6 may be a powerful mechanism to regulate neuronal excitability.
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Affiliation(s)
- Agnes S Zybura
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Anthony J Baucum
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Biology Department, Indiana University-Purdue University Indianapolis, School of Science, Indianapolis, Indiana, USA
| | | | - Theodore R Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Biology Department, Indiana University-Purdue University Indianapolis, School of Science, Indianapolis, Indiana, USA
| | - Andy Hudmon
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA .,Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA
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Pan Y, Xiao Y, Pei Z, Cummins TR. S-Palmitoylation of the sodium channel Nav1.6 regulates its activity and neuronal excitability. J Biol Chem 2020; 295:6151-6164. [PMID: 32161114 DOI: 10.1074/jbc.ra119.012423] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/10/2020] [Indexed: 12/12/2022] Open
Abstract
S-Palmitoylation is a reversible post-translational lipid modification that dynamically regulates protein functions. Voltage-gated sodium channels are subjected to S-palmitoylation and exhibit altered functions in different S-palmitoylation states. Our aim was to investigate whether and how S-palmitoylation regulates Nav1.6 channel function and to identify S-palmitoylation sites that can potentially be pharmacologically targeted. Acyl-biotin exchange assay showed that Nav1.6 is modified by S-palmitoylation in the mouse brain and in a Nav1.6 stable HEK 293 cell line. Using whole-cell voltage clamp, we discovered that enhancing S-palmitoylation with palmitic acid increases Nav1.6 current, whereas blocking S-palmitoylation with 2-bromopalmitate reduces Nav1.6 current and shifts the steady-state inactivation in the hyperpolarizing direction. Three S-palmitoylation sites (Cys1169, Cys1170, and Cys1978) were identified. These sites differentially modulate distinct Nav1.6 properties. Interestingly, Cys1978 is exclusive to Nav1.6 among all Nav isoforms and is evolutionally conserved in Nav1.6 among most species. Cys1978 S-palmitoylation regulates current amplitude uniquely in Nav1.6. Furthermore, we showed that eliminating S-palmitoylation at specific sites alters Nav1.6-mediated excitability in dorsal root ganglion neurons. Therefore, our study reveals S-palmitoylation as a potential isoform-specific mechanism to modulate Nav activity and neuronal excitability in physiological and diseased conditions.
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Affiliation(s)
- Yanling Pan
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Yucheng Xiao
- Department of Biology, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
| | - Zifan Pei
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Theodore R Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Biology, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202; Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202.
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