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Kavanaugh BC, Elacio J, Best CR, St Pierre DG, Pescosolido MF, Ouyang Q, Biedermann J, Bradley RS, Liu JS, Jones RN, Morrow EM. Christianson syndrome across the lifespan: genetic mutations and longitudinal study in children, adolescents, and adults. J Med Genet 2024:jmg-2024-109973. [PMID: 39237363 DOI: 10.1136/jmg-2024-109973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 08/14/2024] [Indexed: 09/07/2024]
Abstract
OBJECTIVES Mutations in the X-linked endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome (CS). Here, in the largest study to date, we examine genetic diversity and clinical progression in CS into adulthood. METHOD Data were collected as part of the International Christianson Syndrome and NHE6 (SLC9A6) Gene Network Study. 44 individuals with 31 unique NHE6 mutations, age 2-32 years, were followed prospectively, herein reporting baseline, 1 year follow-up and retrospective natural history. RESULTS We present data on the CS phenotype with regard to physical growth and adaptive and motor regression across the lifespan including information on mortality. Longitudinal data on body weight and height were examined using a linear mixed model. The rate of growth across development was slow and resulted in prominently decreased age-normed height and weight by adulthood. Adaptive functioning was longitudinally examined; a majority of adult participants (18+ years) lost gross and fine motor skills over a 1 year follow-up. Previously defined core diagnostic criteria for CS (present in>85%)-namely non-verbal status, intellectual disability, epilepsy, postnatal microcephaly, ataxia, hyperkinesia-were universally present in age 6-16; however, an additional core feature of high pain tolerance was added (present in 91%). While neurologic examinations were consistent with cerebellar dysfunction, importantly, a majority of individuals (>50% older than 10) also had corticospinal tract abnormalities. Three participants died during the period of the study. CONCLUSIONS In this large and longitudinal study of CS, we begin to define the trajectory of symptoms and the adult phenotype thereby identifying critical targets for treatment.
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Affiliation(s)
- Brian C Kavanaugh
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Jennifer Elacio
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Carrie R Best
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Danielle G St Pierre
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Matthew F Pescosolido
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Qing Ouyang
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - John Biedermann
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Rebecca S Bradley
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Judy S Liu
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
- Department of Neurology, Rhode Island Hospital, Providence, Rhode Island, USA
| | - Richard N Jones
- Quantitative Sciences Program, Department of Psychiatry and Human Behavior and Department of Neurology, Brown University Warren Alpert Medical School, Providence, Rhode Island, USA
| | - Eric M Morrow
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, Rhode Island, USA
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
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Ma L, Kasula RK, Ouyang Q, Schmidt M, Morrow EM. GGA1 interacts with the endosomal Na+/H+ exchanger NHE6 governing localization to the endosome compartment. J Biol Chem 2024; 300:107552. [PMID: 39002678 PMCID: PMC11375261 DOI: 10.1016/j.jbc.2024.107552] [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: 10/26/2023] [Revised: 06/20/2024] [Accepted: 06/27/2024] [Indexed: 07/15/2024] Open
Abstract
Mutations in the endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome, an X-linked neurological disorder. NHE6 functions in regulation of endosome acidification and maturation in neurons. Using yeast two-hybrid screening with the NHE6 carboxyl terminus as bait, we identify Golgi-associated, gamma adaptin ear-containing, ADP-ribosylation factor (ARF) binding protein 1 (GGA1) as an interacting partner for NHE6. We corroborated the NHE6-GGA1 interaction using: coimmunoprecipitation; overexpressed constructs in mammalian cells; and coimmunoprecipitation of endogenously expressed GGA1 and NHE6 from neuroblastoma cells, as well as from the mouse brain. We demonstrate that GGA1 interacts with organellar NHEs (NHE6, NHE7, and NHE9) and that there is significantly less interaction with cell-surface localized NHEs (NHE1 and NHE5). By constructing hybrid NHE1/NHE6 exchangers, we demonstrate the cytoplasmic tail of NHE6 interacts most strongly with GGA1. We demonstrate the colocalization of NHE6 and GGA1 in cultured, primary hippocampal neurons, using super-resolution microscopy. We test the hypothesis that the interaction of NHE6 and GGA1 functions in the localization of NHE6 to the endosome compartment. Using subcellular fractionation experiments, we show that NHE6 is mislocalized in GGA1 KO cells, wherein we find less NHE6 in endosomes, but more NHE6 transport to lysosomes, and more Golgi retention of NHE6, with increased exocytosis to the surface plasma membrane. Consistent with NHE6 mislocalization, and Golgi retention, we find the intraluminal pH in Golgi to be alkalinized in GGA1-null cells. Our study demonstrates a new interaction between NHE6 and GGA1 which functions in the localization of this intracellular NHE to the endosome compartment.
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Affiliation(s)
- Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Ravi Kiran Kasula
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA.
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Kalm T, Schob C, Völler H, Gardeitchik T, Gilissen C, Pfundt R, Klöckner C, Platzer K, Klabunde-Cherwon A, Ries M, Syrbe S, Beccaria F, Madia F, Scala M, Zara F, Hofstede F, Simon MEH, van Jaarsveld RH, Oegema R, van Gassen KLI, Holwerda SJB, Barakat TS, Bouman A, van Slegtenhorst M, Álvarez S, Fernández-Jaén A, Porta J, Accogli A, Mancardi MM, Striano P, Iacomino M, Chae JH, Jang S, Kim SY, Chitayat D, Mercimek-Andrews S, Depienne C, Kampmeier A, Kuechler A, Surowy H, Bertini ES, Radio FC, Mancini C, Pizzi S, Tartaglia M, Gauthier L, Genevieve D, Tharreau M, Azoulay N, Zaks-Hoffer G, Gilad NK, Orenstein N, Bernard G, Thiffault I, Denecke J, Herget T, Kortüm F, Kubisch C, Bähring R, Kindler S. Etiological involvement of KCND1 variants in an X-linked neurodevelopmental disorder with variable expressivity. Am J Hum Genet 2024; 111:1206-1221. [PMID: 38772379 PMCID: PMC11179411 DOI: 10.1016/j.ajhg.2024.04.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 04/25/2024] [Accepted: 04/25/2024] [Indexed: 05/23/2024] Open
Abstract
Utilizing trio whole-exome sequencing and a gene matching approach, we identified a cohort of 18 male individuals from 17 families with hemizygous variants in KCND1, including two de novo missense variants, three maternally inherited protein-truncating variants, and 12 maternally inherited missense variants. Affected subjects present with a neurodevelopmental disorder characterized by diverse neurological abnormalities, mostly delays in different developmental domains, but also distinct neuropsychiatric signs and epilepsy. Heterozygous carrier mothers are clinically unaffected. KCND1 encodes the α-subunit of Kv4.1 voltage-gated potassium channels. All variant-associated amino acid substitutions affect either the cytoplasmic N- or C-terminus of the channel protein except for two occurring in transmembrane segments 1 and 4. Kv4.1 channels were functionally characterized in the absence and presence of auxiliary β subunits. Variant-specific alterations of biophysical channel properties were diverse and varied in magnitude. Genetic data analysis in combination with our functional assessment shows that Kv4.1 channel dysfunction is involved in the pathogenesis of an X-linked neurodevelopmental disorder frequently associated with a variable neuropsychiatric clinical phenotype.
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Affiliation(s)
- Tassja Kalm
- Institute for Cellular and Integrative Physiology, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Claudia Schob
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Hanna Völler
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Thatjana Gardeitchik
- Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525 GA, the Netherlands
| | - Christian Gilissen
- Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525 GA, the Netherlands
| | - Rolph Pfundt
- Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525 GA, the Netherlands
| | - Chiara Klöckner
- Institute of Human Genetics, University of Leipzig Medical Center, 04103 Leipzig, Germany
| | - Konrad Platzer
- Institute of Human Genetics, University of Leipzig Medical Center, 04103 Leipzig, Germany
| | - Annick Klabunde-Cherwon
- Division of Pediatric Epileptology, Centre for Paediatric and Adolescent Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Markus Ries
- Division of Pediatric Epileptology, Centre for Paediatric and Adolescent Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Steffen Syrbe
- Division of Pediatric Epileptology, Centre for Paediatric and Adolescent Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Francesca Beccaria
- Epilepsy Center, Department of Child Neuropsychiatry, Territorial Social-Health Agency, 46100 Mantova, Italy
| | - Francesca Madia
- Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy
| | - Marcello Scala
- Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16145 Genoa, Italy
| | - Federico Zara
- Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16145 Genoa, Italy
| | - Floris Hofstede
- Department of General Pediatrics, Wilhelmina Children's Hospital, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - Marleen E H Simon
- Department of Clinical Genetics, University Medical Center Utrecht, Utrecht 3584 EA, the Netherlands
| | - Richard H van Jaarsveld
- Department of Clinical Genetics, University Medical Center Utrecht, Utrecht 3584 EA, the Netherlands
| | - Renske Oegema
- Department of Clinical Genetics, University Medical Center Utrecht, Utrecht 3584 EA, the Netherlands
| | - Koen L I van Gassen
- Department of Clinical Genetics, University Medical Center Utrecht, Utrecht 3584 EA, the Netherlands
| | - Sjoerd J B Holwerda
- Department of Clinical Genetics, University Medical Center Utrecht, Utrecht 3584 EA, the Netherlands
| | - Tahsin Stefan Barakat
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam 3000 CA, the Netherlands; ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC University Medical Center, Rotterdam 3000 CA, the Netherlands; Discovery Unit, Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam 3000 CA, the Netherlands
| | - Arjan Bouman
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam 3000 CA, the Netherlands
| | - Marjon van Slegtenhorst
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam 3000 CA, the Netherlands
| | - Sara Álvarez
- Genomics and Medicine, NIMGenetics, 28108 Madrid, Spain
| | - Alberto Fernández-Jaén
- Pediatric Neurology Department, Quironsalud University Hospital Madrid, School of Medicine, European University of Madrid, 28224 Madrid, Spain
| | - Javier Porta
- Genomics, Genologica Medica, 29016 Málaga, Spain
| | - Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre, QC H4A 3J1 Montreal, Canada; Department of Human Genetics, McGill University, QC H4A 3J1 Montreal, Canada
| | | | - Pasquale Striano
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, 16145 Genoa, Italy; Pediatric Neurology and Neuromuscular Diseases Unit, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy
| | - Michele Iacomino
- Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy
| | - Jong-Hee Chae
- Department of Pediatrics, Seoul National University College of Medicine, Seoul 110-744, Republic of Korea; Department of Genomic Medicine, Rare Disease Center, Seoul National University Hospital, Seoul 03080, Republic of Korea
| | - SeSong Jang
- Department of Pediatrics, Seoul National University College of Medicine, Seoul 110-744, Republic of Korea
| | - Soo Y Kim
- Department of Genomic Medicine, Rare Disease Center, Seoul National University Hospital, Seoul 03080, Republic of Korea
| | - David Chitayat
- The Prenatal Diagnosis and Medical Genetics Program, Department of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto ON M5G 1E2 Toronto, Canada; Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for SickKids, University of Toronto, M5G 1X8 Toronto, Canada
| | - Saadet Mercimek-Andrews
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for SickKids, University of Toronto, M5G 1X8 Toronto, Canada; Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, AB T6G 2H7 Edmonton, Canada
| | - Christel Depienne
- Institute of Human Genetics, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
| | - Antje Kampmeier
- Institute of Human Genetics, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
| | - Alma Kuechler
- Institute of Human Genetics, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
| | - Harald Surowy
- Institute of Human Genetics, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
| | | | | | - Cecilia Mancini
- Molecular Genetics and Functional Genomics, Bambino Gesù Children's Hospital, IRCCS, 00146 Rome, Italy
| | - Simone Pizzi
- Molecular Genetics and Functional Genomics, Bambino Gesù Children's Hospital, IRCCS, 00146 Rome, Italy
| | - Marco Tartaglia
- Molecular Genetics and Functional Genomics, Bambino Gesù Children's Hospital, IRCCS, 00146 Rome, Italy
| | - Lucas Gauthier
- Department of Molecular Genetics and Cytogenomics, Rare and Autoinflammatory Diseases Unit, University Hospital of Montpellier, 34295 Montpellier, France
| | - David Genevieve
- Montpellier University, Inserm U1183, Montpellier, France; Department of Clinical Genetics, University Hospital of Montpellier, 34295 Montpellier, France
| | - Mylène Tharreau
- Department of Molecular Genetics and Cytogenomics, Rare and Autoinflammatory Diseases Unit, University Hospital of Montpellier, 34295 Montpellier, France
| | - Noy Azoulay
- The Genetic Institute of Maccabi Health Services, Rehovot 7610000, Israel; Raphael Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva 49100, Israel
| | - Gal Zaks-Hoffer
- Raphael Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva 49100, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nesia K Gilad
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel; Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petah Tikvah 4920235, Israel
| | - Naama Orenstein
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel; Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petah Tikvah 4920235, Israel
| | - Geneviève Bernard
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre, QC H4A 3J1 Montreal, Canada; Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University, Montreal, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, Canada
| | - Isabelle Thiffault
- Genomic Medicine Center, Department of Pediatrics, Children's Mercy Kansas City, Kansas City, MO, USA; UKMC School of Medicine, University of Missouri Kansas City, Kansas City, MO, USA; Department of Pathology and Laboratory Medicine, Children's Mercy Kansas City, Kansas City, MO, USA
| | - Jonas Denecke
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Theresia Herget
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Fanny Kortüm
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Christian Kubisch
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Robert Bähring
- Institute for Cellular and Integrative Physiology, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
| | - Stefan Kindler
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
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He H, Zhang H, Chen H, He F, Yin F, Stauber T, Zou X, Peng J. Functional analysis of two SLC9A6 frameshift variants in lymphoblastoid cells from patients with Christianson syndrome. CNS Neurosci Ther 2023; 29:4059-4069. [PMID: 37381736 PMCID: PMC10651982 DOI: 10.1111/cns.14329] [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: 02/03/2023] [Revised: 05/30/2023] [Accepted: 06/17/2023] [Indexed: 06/30/2023] Open
Abstract
BACKGROUND Christianson syndrome (CS) is caused by mutations in SLC9A6 and is characterized by global developmental delay, epilepsy, hyperkinesis, ataxia, microcephaly, and behavioral disorder. However, the molecular mechanism by which these SLC9A6 mutations cause CS in humans is not entirely understood, and there is no objective method to determine the pathogenicity of single SLC9A6 variants. METHODS Trio-based whole exome sequencing (WES) was carried out on two individuals with suspicion of CS. qRT-PCR, western blot analysis, filipin staining, lysosomal enzymatic assays, and electron microscopy examination, using EBV-LCLs established from the two patients, were performed. RESULTS Trio-based WES identified a hemizygous SLC9A6 c.1560dupT, p.T521Yfs*23 variant in proband 1 and a hemizygous SLC9A6 c.608delA, p.H203Lfs*10 variant in proband 2. Both children exhibited typical phenotypes associated with CS. Expression analysis in EBV-LCLs derived from the two patients showed a significant decrease in mRNA levels and no detectable normal NHE6 protein. EBV-LCLs showed a statistically significant increase in unesterified cholesterol in patient 1, but only non-significant increase in patient 2 when stained with filipin. Activities of lysosomal enzymes (β-hexosaminidase A, β-hexosaminidase A + B, β-galactosidase, galactocerebrosidase, arylsulfatase A) of EBV-LCLs did not significantly differ between the two patients and six controls. Importantly, by electron microscopy we detected an accumulation of lamellated membrane structures, deformed mitochondria, and lipid droplets in the patients' EBV-LCLs. CONCLUSIONS The SLC9A6 p.T521Yfs*23 and p.H203Lfs*10 variants in our patients result in loss of NHE6. Alterations of mitochondria and lipid metabolism may play a role in the pathogenesis of CS. Moreover, the combination of filipin staining with electron microscopy examination of patient lymphoblastoid cells can serve as a useful complementary diagnostic method for CS.
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Affiliation(s)
- Hailan He
- Department of Pediatrics, Xiangya HospitalCentral South UniversityChangshaChina
- Hunan Intellectual and Developmental Disabilities Research CenterChangshaChina
| | - Huiwen Zhang
- Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric ResearchShanghai Jiao Tong University School of MedicineShanghaiChina
| | - Hui Chen
- Department of NeurologyJiangxi Provincial Children's HospitalNanchangChina
| | - Fang He
- Department of Pediatrics, Xiangya HospitalCentral South UniversityChangshaChina
- Hunan Intellectual and Developmental Disabilities Research CenterChangshaChina
| | - Fei Yin
- Department of Pediatrics, Xiangya HospitalCentral South UniversityChangshaChina
- Hunan Intellectual and Developmental Disabilities Research CenterChangshaChina
| | - Tobias Stauber
- Department of Human Medicine and Institute for Molecular MedicineMSH Medical School HamburgHamburgGermany
| | - Xiaomin Zou
- Department of Pediatrics, Xiangya HospitalCentral South UniversityChangshaChina
- Hunan Intellectual and Developmental Disabilities Research CenterChangshaChina
| | - Jing Peng
- Department of Pediatrics, Xiangya HospitalCentral South UniversityChangshaChina
- Hunan Intellectual and Developmental Disabilities Research CenterChangshaChina
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Wu Q, Ma L, Joesch-Cohen L, Schmidt M, Uzun EDG, Morrow EM. Targeting NHE6 gene expression identifies lysosome and neurodevelopmental mechanisms in a haploid in vitro cell model. Biol Open 2023; 12:bio059778. [PMID: 37747131 PMCID: PMC10695175 DOI: 10.1242/bio.059778] [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: 12/02/2022] [Accepted: 09/06/2023] [Indexed: 09/26/2023] Open
Abstract
Christianson syndrome (CS) is an X-linked disorder resulting from loss-of-function (LoF) mutations in SLC9A6 encoding the endosomal Na+/H+ exchanger 6 (NHE6). CS presents with developmental delay, seizures, intellectual disability, nonverbal status, postnatal microcephaly, and ataxia. To define transcriptome signatures of NHE6 LoF, we conducted in-depth RNA-sequencing (RNA-seq) analysis on a haploid NHE6 null cell model. CRIPSR/Cas9 genome editing introduced multiple LoF mutations into SLC9A6 in the near haploid human cell line Hap1. Isogenic, paired parental controls were also studied. NHE6 mutant cell lines were confirmed to have intra-endosomal over-acidification as was seen in other NHE6 null cells. RNA-seq analysis was performed by two widely used pipelines: HISAT2-StringTie-DEseq2 and STAR-HTseq-DEseq2. We identified 1056 differentially expressed genes in mutant NHE6 lines, including genes associated with neurodevelopment, synapse function, voltage-dependent calcium channels, and neuronal signaling. Weighted gene co-expression network analysis was then applied and identified a critical module enriched for genes governing lysosome function. By identifying significantly changed gene expression that is associated with lysosomal mechanisms in NHE6-null cells, our analyses suggest that loss of NHE6 function may converge on mechanisms implicated in lysosome-related neurologic disease. Further, this haploid cell model will serve as an important tool for translational science in CS.
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Affiliation(s)
- Qing Wu
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
| | - Li Ma
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Lena Joesch-Cohen
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
| | - Michael Schmidt
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Ece D. Gamsiz Uzun
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
- Department of Pathology and Laboratory Medicine, Alpert Medical School of Brown University, Providence, RI 02912, USA
| | - Eric M. Morrow
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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Hussain SI, Muhammad N, Shah SUD, Fardous F, Khan SA, Khan N, Rehman AU, Siddique M, Wasan SA, Niaz R, Ullah H, Khan N, Muhammad N, Mirza MU, Wasif N, Khan S. Structural and functional implications of SLC13A3 and SLC9A6 mutations: an in silico approach to understanding intellectual disability. BMC Neurol 2023; 23:353. [PMID: 37794328 PMCID: PMC10548666 DOI: 10.1186/s12883-023-03397-y] [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: 05/24/2023] [Accepted: 09/20/2023] [Indexed: 10/06/2023] Open
Abstract
BACKGROUND Intellectual disability (ID) is a condition that varies widely in both its clinical presentation and its genetic underpinnings. It significantly impacts patients' learning capacities and lowers their IQ below 70. The solute carrier (SLC) family is the most abundant class of transmembrane transporters and is responsible for the translocation of various substances across cell membranes, including nutrients, ions, metabolites, and medicines. The SLC13A3 gene encodes a plasma membrane-localized Na+/dicarboxylate cotransporter 3 (NaDC3) primarily expressed in the kidney, astrocytes, and the choroid plexus. In addition to three Na + ions, it brings four to six carbon dicarboxylates into the cytosol. Recently, it was discovered that patients with acute reversible leukoencephalopathy and a-ketoglutarate accumulation (ARLIAK) carry pathogenic mutations in the SLC13A3 gene, and the X-linked neurodevelopmental condition Christianson Syndrome is caused by mutations in the SLC9A6 gene, which encodes the recycling endosomal alkali cation/proton exchanger NHE6, also called sodium-hydrogen exchanger-6. As a result, there are severe impairments in the patient's mental capacity, physical skills, and adaptive behavior. METHODS AND RESULTS Two Pakistani families (A and B) with autosomal recessive and X-linked intellectual disorders were clinically evaluated, and two novel disease-causing variants in the SLC13A3 gene (NM 022829.5) and the SLC9A6 gene (NM 001042537.2) were identified using whole exome sequencing. Family-A segregated a novel homozygous missense variant (c.1478 C > T; p. Pro493Leu) in the exon-11 of the SLC13A3 gene. At the same time, family-B segregated a novel missense variant (c.1342G > A; p.Gly448Arg) in the exon-10 of the SLC9A6 gene. By integrating computational approaches, our findings provided insights into the molecular mechanisms underlying the development of ID in individuals with SLC13A3 and SLC9A6 mutations. CONCLUSION We have utilized in-silico tools in the current study to examine the deleterious effects of the identified variants, which carry the potential to understand the genotype-phenotype relationships in neurodevelopmental disorders.
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Affiliation(s)
- Syeda Iqra Hussain
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Nazif Muhammad
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Salah Ud Din Shah
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Fardous Fardous
- Department of Medical Lab Technology, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Sher Alam Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Niamatullah Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Adil U Rehman
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Mehwish Siddique
- Department of Zoology, Government Post Graduate College for Women, Satellite Town, Gujranwala, Pakistan
| | - Shoukat Ali Wasan
- Department of Botany, Faculty of Natural Sciences, Shah Abdul Latif University, Khairpur, Sindh, Pakistan
| | - Rooh Niaz
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Hafiz Ullah
- Gomal Center of Biochemistry and Biotechnology (GCBB), Gomal University D. I. Khan, D. I. Khan, Pakistan
| | - Niamat Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Noor Muhammad
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan
| | - Muhammad Usman Mirza
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, N9B 1C4, Canada
| | - Naveed Wasif
- Institute of Human Genetics, Ulm University and Ulm University Medical Center, 89081, Ulm, Germany.
- Institute of Human Genetics, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
| | - Saadullah Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science & Technology (KUST), Kohat, Khyber Pakhtunkhwa, Pakistan.
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7
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Figueroa KP, Anderson CJ, Paul S, Dansithong W, Gandelman M, Scoles DR, Pulst SM. Slc9a6 mutation causes Purkinje cell loss and ataxia in the shaker rat. Hum Mol Genet 2023; 32:1647-1659. [PMID: 36621975 PMCID: PMC10162436 DOI: 10.1093/hmg/ddad004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 12/29/2022] [Accepted: 01/05/2023] [Indexed: 01/10/2023] Open
Abstract
The shaker rat carries a naturally occurring mutation leading to progressive ataxia characterized by Purkinje cell (PC) loss. We previously reported on fine-mapping the shaker locus to the long arm of the rat X chromosome. In this work, we sought to identify the mutated gene underlying the shaker phenotype and confirm its identity by functional complementation. We fine-mapped the candidate region and analyzed cerebellar transcriptomes, identifying a XM_217630.9 (Slc9a6):c.[191_195delinsA] variant in the Slc9a6 gene that segregated with disease. We generated an adeno-associated virus (AAV) targeting Slc9a6 expression to PCs using the mouse L7-6 (L7) promoter. We administered the AAV prior to the onset of PC degeneration through intracerebroventricular injection and found that it reduced the shaker motor, molecular and cellular phenotypes. Therefore, Slc9a6 is mutated in shaker and AAV-based gene therapy may be a viable therapeutic strategy for Christianson syndrome, also caused by Slc9a6 mutation.
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Affiliation(s)
- Karla P Figueroa
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Collin J Anderson
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
- School of Medical Sciences, University of Sydney, Camperdown NSW 2006, Australia
- School of Biomedical Engineering University of Sydney, Darlington NSW 2008, Australia
| | - Sharan Paul
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Warunee Dansithong
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Mandi Gandelman
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Daniel R Scoles
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Stefan M Pulst
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
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8
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Raskoff SZ, Thurm A, Miguel HO, Kim SYH, Quezado ZMN. Pain research and children and adolescents with severe intellectual disability: ethical challenges and imperatives. THE LANCET. CHILD & ADOLESCENT HEALTH 2023; 7:288-296. [PMID: 36563701 PMCID: PMC10038826 DOI: 10.1016/s2352-4642(22)00346-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 11/11/2022] [Accepted: 11/14/2022] [Indexed: 12/24/2022]
Abstract
Children with severe intellectual disabilities encounter inequities in pain-related care, yet little pain research involves this population. A considerable issue with pain research in this population is its ethical complexity. This Viewpoint delineates the ethical challenges of pain research involving children (aged 2-12 years) and adolescents (aged 13-21 years) with severe intellectual disabilities. There are two main issues. First, some of the standard methods for assessing pain and pain sensitivity are not suitable for individuals with severe intellectual disability, who are often non-verbal and unable to understand or follow instructions. Second, children and adolescents with severe intellectual disability cannot provide informed consent or assent to participate in pain research, and their dissent is not always recognised. The existing ethical guidelines for pain research by the International Association for the Study of Pain provide helpful, but general, guidance. This Viewpoint supplements these guidelines and uses a well established framework for assessing the ethics of clinical research to highlight points relevant to designing, doing, reviewing, and evaluating research involving children and adolescents with severe intellectual disability, focusing on issues that are unaddressed in existing guidance.
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Affiliation(s)
- Sarah Z Raskoff
- Uehiro Centre for Practical Ethics, University of Oxford, Oxford, UK.
| | - Audrey Thurm
- Office of the Clinical Director, National Institute of Mental Health, Bethesda, MD, USA
| | - Helga O Miguel
- Department of Perioperative Medicine, The Clinical Center, National Institute of Mental Health, Bethesda, MD, USA
| | - Scott Y H Kim
- Department of Bioethics, National Institute of Mental Health, Bethesda, MD, USA
| | - Zenaide M N Quezado
- Department of Perioperative Medicine, The Clinical Center, National Institute of Mental Health, Bethesda, MD, USA
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9
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Altered distribution and localization of organellar Na +/H + exchangers in postmortem schizophrenia dorsolateral prefrontal cortex. Transl Psychiatry 2023; 13:34. [PMID: 36732328 PMCID: PMC9895429 DOI: 10.1038/s41398-023-02336-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/20/2023] [Accepted: 01/24/2023] [Indexed: 02/04/2023] Open
Abstract
Schizophrenia is a complex and multifactorial disorder associated with altered neurotransmission as well as numerous signaling pathway and protein trafficking disruptions. The pH of intracellular organelles involved in protein trafficking is tightly regulated and impacts their functioning. The SLC9A family of Na+/H+ exchangers (NHEs) plays a fundamental role in cellular and intracellular pH homeostasis. Four organellar NHE isoforms (NHE6-NHE9) are targeted to intracellular organelles involved in protein trafficking. Increased interactions between organellar NHEs and receptor of activated protein C kinase 1 (RACK1) can lead to redistribution of NHEs to the plasma membrane and hyperacidification of target organelles. Given their role in organelle pH regulation, altered expression and/or localization of organellar NHEs could be an underlying cellular mechanism contributing to abnormal intracellular trafficking and disrupted neurotransmitter systems in schizophrenia. We thus characterized organellar NHE expression, co-immunoprecipitation with RACK1, and Triton X-114 (TX-114) phase partitioning in dorsolateral prefrontal cortex of 25 schizophrenia and 25 comparison subjects by Western blot analysis. In schizophrenia after controlling for subject age at time of death, postmortem interval, tissue pH, and sex, there was significantly decreased total expression of NHE8, decreased co-immunoprecipitation of NHE8 (64%) and NHE9 (56%) with RACK1, and increased TX-114 detergent phase partitioning of NHE6 (283%), NHE9 (75%), and RACK1 (367%). Importantly, none of these dependent measures was significantly impacted when comparing those in the schizophrenia group on antipsychotics to those off of antipsychotics for at least 6 weeks at their time of death and none of these same proteins were affected in rats chronically treated with haloperidol. In summary, we characterized organellar NHE expression and distribution in schizophrenia DLPFC and identified abnormalities that could represent a novel mechanism contributing to disruptions in protein trafficking and neurotransmission in schizophrenia.
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10
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Dong Y, Lian R, Jin L, Zhao S, Tao W, Wang L, Li M, Jia T, Chen X, Cao S. Clinical and genetic analysis of Christianson syndrome caused by variant of SLC9A6: case report and literature review. Front Neurol 2023; 14:1152696. [PMID: 37213903 PMCID: PMC10196350 DOI: 10.3389/fneur.2023.1152696] [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: 02/01/2023] [Accepted: 04/18/2023] [Indexed: 05/23/2023] Open
Abstract
Background Intellectual disability, X-linked, syndromic, Christianson type (MRXSCH, OMIM: 300243)-known as Christianson syndrome (CS)-is characterized by microcephaly, epilepsy, ataxia, and absence of verbal language ability. CS is attributed to mutations in the solute carrier family 9 member A6 gene (SLC9A6). Materials and methods This study reports the case of a boy 1 year and 3 months of age who was diagnosed with CS in our department. Genetic etiology was determined by whole-exome sequencing, and a minigene splicing assay was used to verify whether the mutation affected splicing. A literature review of CS cases was conducted and the clinical and genetic features were summarized. Results The main clinical manifestations of CS include seizures, developmental regression, and exceptional facial features. Whole-exome sequencing revealed a de novo splice variant in intron 11 (c.1366 + 1G > C) of SLC9A6. The mutation produced two abnormal mRNA products (verified by a minigene splicing assay), resulting in the formation of truncated protein. A total of 95 CS cases were identified in the literature, with various symptoms, such as delayed intellectual development (95/95, 100.00%), epilepsy (87/88, 98.86%), and absent verbal language (75/83, 90.36%). At least 50 pathogenic variants of SLC9A6 have been identified, with the highest frequency observed in exon 12. Conclusion Our patient is the first case with the c.1366 + 1G > C variant of SLC9A6 in CS. The summary of known cases can serve as a reference for analyzing the mutation spectrum and pathogenesis of CS.
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Affiliation(s)
- Yan Dong
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- Henan Key Laboratory of Child Brain Injury and Henan Pediatric Clinical Research Center, The Third Affiliated Hospital and Institute of Neuroscience, Zhengzhou, China
- *Correspondence: Yan Dong,
| | - Ruofei Lian
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Liang Jin
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shichao Zhao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Wenpeng Tao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Lijun Wang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Mengchun Li
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Tianming Jia
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Xuejing Chen
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shushi Cao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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11
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Bernardazzi C, Sheikh IA, Xu H, Ghishan FK. The Physiological Function and Potential Role of the Ubiquitous Na +/H + Exchanger Isoform 8 (NHE8): An Overview Data. Int J Mol Sci 2022; 23:ijms231810857. [PMID: 36142772 PMCID: PMC9501935 DOI: 10.3390/ijms231810857] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 09/08/2022] [Accepted: 09/15/2022] [Indexed: 11/16/2022] Open
Abstract
The Na+/H+ exchanger transporters (NHE) play an important role in various biologic processes including Na+ absorption, intracellular pH homeostasis, cell volume regulation, proliferation, and apoptosis. The wide expression pattern and cellular localization of NHEs make these proteins pivotal players in virtually all human tissues and organs. In addition, recent studies suggest that NHEs may be one of the primeval transport protein forms in the history of life. Among the different isoforms, the most well-characterized NHEs are the Na+/H+ exchanger isoform 1 (NHE1) and Na+/H+ exchanger isoform 3 (NHE3). However, Na+/H+ exchanger isoform 8 (NHE8) has been receiving attention based on its recent discoveries in the gastrointestinal tract. In this review, we will discuss what is known about the physiological function and potential role of NHE8 in the main organ systems, including useful overviews that could inspire new studies on this multifaceted protein.
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12
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Lee Y, Miller MR, Fernandez MA, Berg EL, Prada AM, Ouyang Q, Schmidt M, Silverman JL, Young-Pearse TL, Morrow EM. Early lysosome defects precede neurodegeneration with amyloid-β and tau aggregation in NHE6-null rat brain. Brain 2022; 145:3187-3202. [PMID: 34928329 PMCID: PMC10147331 DOI: 10.1093/brain/awab467] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 10/25/2021] [Accepted: 11/24/2021] [Indexed: 11/12/2022] Open
Abstract
Loss-of-function mutations in the X-linked endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome in males. Christianson syndrome involves endosome dysfunction leading to early cerebellar degeneration, as well as later-onset cortical and subcortical neurodegeneration, potentially including tau deposition as reported in post-mortem studies. In addition, there is reported evidence of modulation of amyloid-β levels in experimental models wherein NHE6 expression was targeted. We have recently shown that loss of NHE6 causes defects in endosome maturation and trafficking underlying lysosome deficiency in primary mouse neurons in vitro. For in vivo studies, rat models may have an advantage over mouse models for the study of neurodegeneration, as rat brain can demonstrate robust deposition of endogenously-expressed amyloid-β and tau in certain pathological states. Mouse models generally do not show the accumulation of insoluble, endogenously-expressed (non-transgenic) tau or amyloid-β. Therefore, to study neurodegeneration in Christianson syndrome and the possibility of amyloid-β and tau pathology, we generated an NHE6-null rat model of Christianson syndrome using CRISPR-Cas9 genome-editing. Here, we present the sequence of pathogenic events in neurodegenerating NHE6-null male rat brains across the lifespan. NHE6-null rats demonstrated an early and rapid loss of Purkinje cells in the cerebellum, as well as a more protracted neurodegenerative course in the cerebrum. In both the cerebellum and cerebrum, lysosome deficiency is an early pathogenic event, preceding autophagic dysfunction. Microglial and astrocyte activation also occur early. In the hippocampus and cortex, lysosome defects precede loss of pyramidal cells. Importantly, we subsequently observed biochemical and in situ evidence of both amyloid-β and tau aggregation in the aged NHE6-null hippocampus and cortex (but not in the cerebellum). Tau deposition is widely distributed, including cortical and subcortical distributions. Interestingly, we observed tau deposition in both neurons and glia, as has been reported in Christianson syndrome post-mortem studies previously. In summary, this experimental model is among very few examples of a genetically modified animal that exhibits neurodegeneration with deposition of endogenously-expressed amyloid-β and tau. This NHE6-null rat will serve as a new robust model for Christianson syndrome. Furthermore, these studies provide evidence for linkages between endolysosome dysfunction and neurodegeneration involving protein aggregations, including amyloid-β and tau. Therefore these studies may provide insight into mechanisms of more common neurodegenerative disorders, including Alzheimer's disease and related dementias.
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Affiliation(s)
- YouJin Lee
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Morgan R Miller
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Marty A Fernandez
- Ann Romney Center for Neurologic Diseases, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
| | - Elizabeth L Berg
- MIND Institute and Department of Psychiatry and Behavioural Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - Adriana M Prada
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Jill L Silverman
- MIND Institute and Department of Psychiatry and Behavioural Sciences, University of California Davis School of Medicine, Sacramento, CA, USA
| | - Tracy L Young-Pearse
- Ann Romney Center for Neurologic Diseases, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
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13
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Fernandez MA, Bah F, Ma L, Lee Y, Schmidt M, Welch E, Morrow EM, Young-Pearse TL. Loss of endosomal exchanger NHE6 leads to pathological changes in tau in human neurons. Stem Cell Reports 2022; 17:2111-2126. [PMID: 36055242 PMCID: PMC9481919 DOI: 10.1016/j.stemcr.2022.08.001] [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: 01/17/2022] [Revised: 08/03/2022] [Accepted: 08/03/2022] [Indexed: 12/09/2022] Open
Abstract
Disruption of endolysosomal and autophagy-lysosomal systems is increasingly implicated in neurodegeneration. Sodium-proton exchanger 6 (NHE6) contributes to the maintenance of proper endosomal pH, and loss-of function mutations in the X-linked NHE6 lead to Christianson syndrome (CS) in males. Neurodegenerative features of CS are increasingly recognized, with postmortem and clinical data implicating a role for tau. We generated cortical neurons from NHE6 knockout (KO) and isogenic wild-type control human induced pluripotent stem cells. We report elevated phosphorylated and sarkosyl-insoluble tau in NHE6 KO neurons. We demonstrate that NHE6 KO leads to lysosomal and autophagy dysfunction involving reduced lysosomal number and protease activity, diminished autophagic flux, and p62 accumulation. Finally, we show that treatment with trehalose or rapamycin, two enhancers of autophagy-lysosomal function, each partially rescue this tau phenotype. We provide insight into the neurodegenerative processes underlying NHE6 loss of function and into the broader role of the endosome-lysosome-autophagy network in neurodegeneration.
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Affiliation(s)
- Marty A Fernandez
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Fatmata Bah
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - YouJin Lee
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA
| | - Elizabeth Welch
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science (BITS), Brown University, Providence, RI 02912, USA; Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University, Providence, RI 02912, USA.
| | - Tracy L Young-Pearse
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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Anderegg MA, Gyimesi G, Ho TM, Hediger MA, Fuster DG. The Less Well-Known Little Brothers: The SLC9B/NHA Sodium Proton Exchanger Subfamily—Structure, Function, Regulation and Potential Drug-Target Approaches. Front Physiol 2022; 13:898508. [PMID: 35694410 PMCID: PMC9174904 DOI: 10.3389/fphys.2022.898508] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/04/2022] [Indexed: 12/15/2022] Open
Abstract
The SLC9 gene family encodes Na+/H+ exchangers (NHEs), a group of membrane transport proteins critically involved in the regulation of cytoplasmic and organellar pH, cell volume, as well as systemic acid-base and volume homeostasis. NHEs of the SLC9A subfamily (NHE 1–9) are well-known for their roles in human physiology and disease. Much less is known about the two members of the SLC9B subfamily, NHA1 and NHA2, which share higher similarity to prokaryotic NHEs than the SLC9A paralogs. NHA2 (also known as SLC9B2) is ubiquitously expressed and has recently been shown to participate in renal blood pressure and electrolyte regulation, insulin secretion and systemic glucose homeostasis. In addition, NHA2 has been proposed to contribute to the pathogenesis of polycystic kidney disease, the most common inherited kidney disease in humans. NHA1 (also known as SLC9B1) is mainly expressed in testis and is important for sperm motility and thus male fertility, but has not been associated with human disease thus far. In this review, we present a summary of the structure, function and regulation of expression of the SLC9B subfamily members, focusing primarily on the better-studied SLC9B paralog, NHA2. Furthermore, we will review the potential of the SLC9B subfamily as drug targets.
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Affiliation(s)
- Manuel A. Anderegg
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- *Correspondence: Manuel A. Anderegg,
| | - Gergely Gyimesi
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Membrane Transport Discovery Lab, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Tin Manh Ho
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Matthias A. Hediger
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Membrane Transport Discovery Lab, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Daniel G. Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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15
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Gao AYL, Lourdin-De Filippis E, Orlowski J, McKinney RA. Roles of Endomembrane Alkali Cation/Proton Exchangers in Synaptic Function and Neurodevelopmental Disorders. Front Physiol 2022; 13:892196. [PMID: 35547574 PMCID: PMC9081726 DOI: 10.3389/fphys.2022.892196] [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: 03/08/2022] [Accepted: 03/30/2022] [Indexed: 12/25/2022] Open
Abstract
Endomembrane alkali cation (Na+, K+)/proton (H+) exchangers (eNHEs) are increasingly associated with neurological disorders. These eNHEs play integral roles in regulating the luminal pH, processing, and trafficking of cargo along the secretory (Golgi and post-Golgi vesicles) and endocytic (early, recycling, and late endosomes) pathways, essential regulatory processes vital for neuronal development and plasticity. Given the complex morphology and compartmentalization of multipolar neurons, the contribution of eNHEs in maintaining optimal pH homeostasis and cargo trafficking is especially significant during periods of structural and functional development and remodeling. While the importance of eNHEs has been demonstrated in a variety of non-neuronal cell types, their involvement in neuronal function is less well understood. In this review, we will discuss their emerging roles in excitatory synaptic function, particularly as it pertains to cellular learning and remodeling. We will also explore their connections to neurodevelopmental conditions, including intellectual disability, autism, and attention deficit hyperactivity disorders.
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Affiliation(s)
- Andy Y L Gao
- Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.,Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
| | | | - John Orlowski
- Department of Physiology, McGill University, Montreal, QC, Canada
| | - R Anne McKinney
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
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16
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Donor Splice Site Variant in SLC9A6 Causes Christianson Syndrome in a Lithuanian Family: A Case Report. MEDICINA (KAUNAS, LITHUANIA) 2022; 58:medicina58030351. [PMID: 35334527 PMCID: PMC8949093 DOI: 10.3390/medicina58030351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/17/2022] [Accepted: 02/24/2022] [Indexed: 11/16/2022]
Abstract
Background and Objectives: The pathogenic variants of SLC9A6 are a known cause of a rare, X-linked neurological disorder called Christianson syndrome (CS). The main characteristics of CS are developmental delay, intellectual disability, and neurological findings. This study investigated the genetic basis and explored the molecular changes that led to CS in two male siblings presenting with intellectual disability, epilepsy, behavioural problems, gastrointestinal dysfunction, poor height, and weight gain. Materials and Methods: Next-generation sequencing of a tetrad was applied to identify the DNA changes and Sanger sequencing of proband’s cDNA was used to evaluate the impact of a splice site variant on mRNA structure. Bioinformatical tools were used to investigate SLC9A6 protein structure changes. Results: Sequencing and bioinformatical analysis revealed a novel donor splice site variant (NC_000023.11(NM_001042537.1):c.899 + 1G > A) that leads to a frameshift and a premature stop codon. Protein structure modelling showed that the truncated protein is unlikely to form any functionally relevant SLC9A6 dimers. Conclusions: Molecular and bioinformatical analysis revealed the impact of a novel donor splice site variant in the SLC9A6 gene that leads to truncated and functionally disrupted protein causing the phenotype of CS in the affected individuals.
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17
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Liu X, Xie L, Fang Z, Jiang L. Case Report: Novel SLC9A6 Splicing Variant in a Chinese Boy With Christianson Syndrome With Electrical Status Epilepticus During Sleep. Front Neurol 2022; 12:796283. [PMID: 35095740 PMCID: PMC8795361 DOI: 10.3389/fneur.2021.796283] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 12/17/2021] [Indexed: 12/30/2022] Open
Abstract
We investigated the existence and potential pathogenicity of a SLC9A6 splicing variant in a Chinese boy with Christianson Syndrome (CS), which was reported for the first time in China. Trio whole-exome sequencing (WES) was performed in the proband and his parents. Multiple computer prediction tools were used to evaluate the pathogenicity of the variant, and reverse transcription-polymerase chain reaction (RT-PCR) analysis and cDNA sequencing were performed to verify the RNA splicing results. The patient presented with characteristic features of CS: global developmental delay, seizures, absent speech, truncal ataxia, microcephaly, ophthalmoplegia, smiling face and hyperkinesis with electrical status epilepticus during sleep (ESES) detected in an electroencephalogram (EEG). A SLC9A6 splicing variant was identified by WES and complete skipping of exon 10 was confirmed by RT-PCR. This resulted in altered gene function and was predicted to be pathogenic. ESES observed early in the disease course is considered to be a significant feature of CS with the SLC9A6 variant. Combined genetic analysis at both the DNA and RNA levels is necessary to confirm the pathogenicity of this variant and its role in the clinical diagnosis of CS.
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18
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Bastos Ferreira AP, do Nascimento ADFS, Sampaio Rocha-Filho PA. Cerebral and spinal cord changes observed through magnetic resonance imaging in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis: a systematic review. J Neurovirol 2022; 28:1-16. [PMID: 34981435 DOI: 10.1007/s13365-021-01043-2] [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: 05/01/2021] [Revised: 11/21/2021] [Accepted: 12/09/2021] [Indexed: 11/27/2022]
Abstract
To verify brain and spinal changes using magnetic resonance imaging in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis. This was a systematic review. The descriptors used were tropical spastic paraparesis and magnetic resonance image. The keyword HTLV-1-associated myelopathy was also used. Twenty-three articles were included: 16 detected brain changes and 18 detected spinal changes. White matter lesions were the most frequent finding in the brain. Brain injuries were most frequently identified in the periventricular region, in the subcortical region, in the centrum semiovale, in the brain stem, and corpus callosum. Atrophy was the most frequent finding of the spinal cord, affecting the thoracic and cervical regions, and was associated with a longer evolution of myelopathy. White matter lesions in these regions were also observed. Cortical white matter lesions and thoracic spinal cord atrophy were the most frequently reported changes in patients with HTLV-1-associated myelopathy.
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Affiliation(s)
- Ana Patrícia Bastos Ferreira
- Post-Graduation Program in Neuropsychiatry and Behavioral Sciences (Posneuro), Federal University of Pernambuco (UFPE), Recife, Brazil.,Rua Carlos Pereira Falcão, 1136, Recife, 51021-350, Brazil
| | - Ana Dolores Firmino Santos do Nascimento
- Post-Graduation Program in Neuropsychiatry and Behavioral Sciences (Posneuro), Federal University of Pernambuco (UFPE), Recife, Brazil.,Rua Arlindo Gouveia, 145, Recife, 50720-595, Brazil
| | - Pedro Augusto Sampaio Rocha-Filho
- Division of Neuropsychiatry, Federal University of Pernambuco (UFPE), Recife, Brazil. .,Rua General Joaquim Inácio, Pernambuco- CEP, 1412 - Edifício The Plaza Business Center, Recife, Sala, 83052011-270, Brazil.
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19
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Lan Y, Yi S, Li M, Wang J, Yang Q, Yi S, Chen F, Huang L, Ruan Y, Shen Y, Luo J, Qin Z. Case Report: Christianson Syndrome Caused by SLC9A6 Mutation: From Case to Genotype-Phenotype Analysis. Front Genet 2021; 12:783841. [PMID: 34987551 PMCID: PMC8721738 DOI: 10.3389/fgene.2021.783841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/30/2021] [Indexed: 11/13/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked neurodevelopmental syndrome characterized by microcephaly, epilepsy, ataxia, and severe generalized developmental delay. Pathogenic mutations in the SLC9A6 gene, which encodes the Na+/H+ exchanger protein member 6 (NHE6), are associated with CS and autism spectrum disorder in males. In this study, whole exome sequencing (WES) and Sanger sequencing revealed a novel de novo frameshift variant c.1548_1549insT of SLC9A6 in a 14-month-old boy with early-onset seizures. According to The American College of Medical Genetics and Genomics (ACMG)/the Association for Molecular Pathology (AMP) guidelines, the variant was classified as pathogenic. The proband presented with several core symptoms of typical epilepsy, including microcephaly, motor delay, distal muscle weakness, micrognathia, occasional unprovoked laughter, swallowing and speech difficulties. Electroencephalography (EEG) showed spikes-slow waves in frontal pole, frontal, anterior temporal and frontal midline point areas. Gesell development schedules (GDS) indicated generalized developmental delay. We also summarized all the reported variants and analyzed the correlation of genotype and phenotype of CS. Our study extends the mutation spectrum of the SLC9A6 gene, and it might imply that the phenotypes of CS are not correlated with SLC9A6 genotypes.
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Affiliation(s)
- Yueyun Lan
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Sheng Yi
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Mengting Li
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
- The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Jinqiu Wang
- Pediatrics Department, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Qi Yang
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Shang Yi
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Fei Chen
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Limei Huang
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
| | - Yiyan Ruan
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Yiping Shen
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
- Department of Genetics, Harvard Medical School, Boston, MA, United States
| | - Jingsi Luo
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
- *Correspondence: Jingsi Luo, ; Zailong Qin,
| | - Zailong Qin
- Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Guangxi Key Laboratory of Precision Medicine for Genetic Diseases, Guangxi Key Laboratory of Birth Defects and Stem Cell Biobank, Guangxi Key Laboratory of Birth Defects Research and Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
- Genetic and Metabolic Central Laboratory, Guangxi Birth Defects Research and Prevention Institute, Nanning, China
- *Correspondence: Jingsi Luo, ; Zailong Qin,
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20
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Gruber R, Scholes S, Bertone A, McKinney RA, Orlowski J, Wise MS. Sleep and daytime behavior in individuals with Christianson Syndrome. Sleep Med 2021; 89:55-59. [PMID: 34883399 DOI: 10.1016/j.sleep.2021.11.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 11/09/2021] [Accepted: 11/13/2021] [Indexed: 11/29/2022]
Abstract
BACKGROUND The objectives of this study were to: 1) characterize the sleep behaviors and symptoms of individuals with Christianson Syndrome (CS) by means of validated questionnaires; and 2) determine their associations with daytime emotional and behavioral symptoms in this population. METHODS Participants included 16 boys genetically diagnosed with CS, between 2.5 and 40 years of age (M = 14.5 ± 8.08). Parents completed questionnaires regarding the sleep, daytime behavior, and health of their child. RESULTS Of the participants, 31% did not obtain the recommended amount of sleep for their age, 43% experienced a prolonged sleep latency, and 88% had a clinical or sub-clinical score for at least one subscale of the Sleep Disturbance Scale for Children (SDSC). Specific problems detected included insomnia, sleep-wake transition disorders, periodic limb movements in sleep, and sleep related breathing disorders. About half of the participants manifested emotional and behavioral problems at clinical levels. Higher levels of sleep disturbances were associated with higher levels of behavioral and emotional daytime symptoms. CONCLUSIONS Sleep problems are common in individuals with CS and are associated with daytime behavioral and emotional symptoms.
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Affiliation(s)
- Reut Gruber
- Attention, Behavior and Sleep Laboratory, Douglas Hospital Research Centre, Montreal, Quebec, Canada; Department of Psychiatry, McGill University, Montréal, Québec, Canada.
| | - Samantha Scholes
- Attention, Behavior and Sleep Laboratory, Douglas Hospital Research Centre, Montreal, Quebec, Canada; Perceptual Neuroscience Lab (PNLab) for Autism, Development Department of Educational and Counselling Psychology, McGill University, Montréal, Québec, Canada
| | - Armando Bertone
- Perceptual Neuroscience Lab (PNLab) for Autism, Development Department of Educational and Counselling Psychology, McGill University, Montréal, Québec, Canada
| | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Québec, Canada
| | - Merrill S Wise
- Mid-South Pulmonary and Sleep Specialists, Memphis, TN, USA
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21
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Zhang X, Wu X, Liu H, Song T, Jiang Y, He H, Yang S, Xie Y. Christianson syndrome: A novel splicing variant of SLC9A6 causes exon skipping in a Chinese boy and a literature review. J Clin Lab Anal 2021; 36:e24123. [PMID: 34791706 PMCID: PMC8761434 DOI: 10.1002/jcla.24123] [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: 09/17/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Variants in the endosomal solute carrier family 9 member A6 (SLC9A6)/(Na+ ,K+ )/H+ exchanger 6 (NHE6) gene have been linked to epilepsy, speech loss, truncal ataxia, hyperkinesia, and postnatal microcephaly. METHODS In the present study, we evaluated genetic alterations in a 3-year-old Chinese boy displayed features of epilepsy, psychomotor retardation, microcephaly, low body weight, difficulty in feeding, excessive movement, attention loss, ataxia, and cerebellar atrophy and his healthy family using WES method. The identified variant was further confirmed by Sanger sequencing method. Finally, minigene assays were used to verify whether the novel SLC9A6 intronic variant influenced the normal splicing of mRNA. RESULTS We identified a novel hemizygous splicing variant [NM_001042537.1: c.1463-1G>A] in SLC9A6 by trio-based exome sequencing. The minigene expression in vitro confirmed the splicing variant altered a consensus splice acceptor site of SLC9A6 intron 11, resulting in skipping over exon 12. CONCLUSIONS Our finding extends the catalog of pathogenic intronic variants affecting SLC9A6 pre-mRNA splicing and provides a basis for the genetic diagnosis of CS.
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Affiliation(s)
- Xiaoge Zhang
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Xiaofang Wu
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Hongli Liu
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Tingting Song
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Yongsheng Jiang
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Hanhan He
- Department of pediatrics, Northwest Women's and Children's Hospital, Xi'an, China
| | - Shaoqing Yang
- State Key Laboratory of Military Stomatology, Department of Oral Biology, School of Stomatology, Clinic of Oral Rare and Genetic Diseases, National Clinical Research Center for Oral Diseases, The Fourth Military Medical University, Xi'an, China
| | - Yun Xie
- Department of clinical laboratory, Northwest Women's and Children's Hospital, Xi'an, China
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22
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Loss of Christianson Syndrome Na +/H + Exchanger 6 (NHE6) Causes Abnormal Endosome Maturation and Trafficking Underlying Lysosome Dysfunction in Neurons. J Neurosci 2021; 41:9235-9256. [PMID: 34526390 PMCID: PMC8570832 DOI: 10.1523/jneurosci.1244-20.2021] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/05/2021] [Accepted: 08/07/2021] [Indexed: 01/08/2023] Open
Abstract
Loss-of-function mutations in endosomal Na+/H+ exchanger 6 (NHE6) cause the X-linked neurologic disorder Christianson syndrome. Patients exhibit symptoms associated with both neurodevelopmental and neurodegenerative abnormalities. While loss of NHE6 has been shown to overacidify the endosome lumen, and is associated with endolysosome neuropathology, NHE6-mediated mechanisms in endosome trafficking and lysosome function have been understudied. Here, we show that NHE6-null mouse neurons demonstrate worsening lysosome function with time in culture, likely as a result of defective endosome trafficking. NHE6-null neurons exhibit overall reduced lysosomal proteolysis despite overacidification of the endosome and lysosome lumen. Akin to Nhx1 mutants in Saccharomyces cerevisiae, we observe decreased endosome-lysosome fusion in NHE6-null neurons. Also, we find premature activation of pH-dependent cathepsin D (CatD) in endosomes. While active CatD is increased in endosomes, CatD activation and CatD protein levels are reduced in the lysosome. Protein levels of another mannose 6-phosphate receptor (M6PR)-dependent enzyme, β-N-acetylglucosaminidase, were also decreased in lysosomes of NHE6-null neurons. M6PRs accumulate in late endosomes, suggesting defective M6PR recycling and retromer function in NHE6-null neurons. Finally, coincident with decreased endosome-lysosome fusion, using total internal reflection fluorescence, we also find a prominent increase in fusion between endosomal multivesicular bodies and the plasma membrane, indicating enhanced exosome secretion from NHE6-null neurons. In summary, in addition to overacidification of endosomes and lysosomes, loss of NHE6 leads to defects in endosome maturation and trafficking, including enhanced exosome release, contributing to lysosome deficiency and potentially leading to neurodegenerative disease. SIGNIFICANCE STATEMENT Loss-of-function mutations in the endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome, an X-linked neurologic disorder. Loss of NHE6 has been shown to overacidify endosomes; however, endosome trafficking mechanisms have been understudied, and the mechanisms leading to neurodegeneration are largely unknown. In NHE6-null mouse neurons in vitro, we find worsening lysosome function with days in culture. Notably, pH-dependent lysosome enzymes, such as cathepsin D, have reduced activity in lysosomes yet increased, precocious activity in endosomes in NHE6-null neurons. Further, endosomes show reduced fusion to lysosomes, and increased fusion to the plasma membrane with increased exosome release. This study identifies new mechanisms involving defective endosome maturation and trafficking that impair lysosome function in Christianson syndrome, likely contributing to neurodegeneration.
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Lizarraga SB, Ma L, Maguire AM, van Dyck LI, Wu Q, Ouyang Q, Kavanaugh BC, Nagda D, Livi LL, Pescosolido MF, Schmidt M, Alabi S, Cowen MH, Brito-Vargas P, Hoffman-Kim D, Gamsiz Uzun ED, Schlessinger A, Jones RN, Morrow EM. Human neurons from Christianson syndrome iPSCs reveal mutation-specific responses to rescue strategies. Sci Transl Med 2021; 13:13/580/eaaw0682. [PMID: 33568516 DOI: 10.1126/scitranslmed.aaw0682] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 06/04/2020] [Accepted: 09/18/2020] [Indexed: 12/16/2022]
Abstract
Christianson syndrome (CS), an X-linked neurological disorder characterized by postnatal attenuation of brain growth (postnatal microcephaly), is caused by mutations in SLC9A6, the gene encoding endosomal Na+/H+ exchanger 6 (NHE6). To hasten treatment development, we established induced pluripotent stem cell (iPSC) lines from patients with CS representing a mutational spectrum, as well as biologically related and isogenic control lines. We demonstrated that pathogenic mutations lead to loss of protein function by a variety of mechanisms: The majority of mutations caused loss of mRNA due to nonsense-mediated mRNA decay; however, a recurrent, missense mutation (the G383D mutation) had both loss-of-function and dominant-negative activities. Regardless of mutation, all patient-derived neurons demonstrated reduced neurite growth and arborization, likely underlying diminished postnatal brain growth in patients. Phenotype rescue strategies showed mutation-specific responses: A gene transfer strategy was effective in nonsense mutations, but not in the G383D mutation, wherein residual protein appeared to interfere with rescue. In contrast, application of exogenous trophic factors (BDNF or IGF-1) rescued arborization phenotypes across all mutations. These results may guide treatment development in CS, including gene therapy strategies wherein our data suggest that response to treatment may be dictated by the class of mutation.
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Affiliation(s)
- Sofia B Lizarraga
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.,Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC 29208, USA
| | - Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
| | - Abbie M Maguire
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, RI 02912, USA
| | - Laura I van Dyck
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Qing Wu
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA.,Center for Computational Molecular Biology, Brown University, Providence, RI 02912, USA
| | - Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
| | - Brian C Kavanaugh
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, RI 02912, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
| | - Dipal Nagda
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Liane L Livi
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Matthew F Pescosolido
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, RI 02912, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, RI 02912, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
| | - Shanique Alabi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Mara H Cowen
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.,Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC 29208, USA
| | - Paul Brito-Vargas
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.,Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC 29208, USA
| | - Diane Hoffman-Kim
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, RI 02912, USA.,Center for Biomedical Engineering, Brown University, Providence, RI 02912, USA
| | - Ece D Gamsiz Uzun
- Center for Computational Molecular Biology, Brown University, Providence, RI 02912, USA.,Department of Pathology and Laboratory Medicine, Warren Alpert Medical School of Brown University, Providence, RI 02912, USA
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Richard N Jones
- Quantitative Sciences Program, Department of Psychiatry and Human Behavior and Department of Neurology, Warren Alpert Medical School of Brown University, Providence, RI 02912, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA. .,Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, RI 02912, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
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Ma L, Schmidt M, Morrow EM. Human iPSC lines from a Christianson syndrome patient with NHE6 W523X mutation, a biologically-related control, and CRISPR/Cas9 gene-corrected isogenic controls. Stem Cell Res 2021; 54:102435. [PMID: 34182254 PMCID: PMC8375322 DOI: 10.1016/j.scr.2021.102435] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 06/15/2021] [Indexed: 11/30/2022] Open
Abstract
Loss-of-function mutations in Na+/H + exchanger 6 (NHE6) (also termed SLC9A6) cause the X-linked neurogenetic disorder Christianson syndrome (CS). Using peripheral blood mononuclear cells, we developed induced pluripotent stem cell (iPSC) lines from a patient with the NHE6 nonsense mutation c.1569G > A (p. (W523X)) and diagnosed with CS and from a biologically-related control. Using CRISPR/Cas9 gene editing, we generated two isogenic control lines in which the c.1569G > A mutation was corrected. All lines were verified by DNA sequencing and for NHE6 protein expression, pluripotency, and differentiation potential. These lines will serve as a valuable resource for both basic and translational studies in CS.
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Affiliation(s)
- Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA; Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA; Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA; Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA; Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Emma Pendleton Bradley Hospital, East Providence, RI 02915, USA.
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SCAMP5 plays a critical role in axonal trafficking and synaptic localization of NHE6 to adjust quantal size at glutamatergic synapses. Proc Natl Acad Sci U S A 2021; 118:2011371118. [PMID: 33372133 DOI: 10.1073/pnas.2011371118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Glutamate uptake into synaptic vesicles (SVs) depends on cation/H+ exchange activity, which converts the chemical gradient (ΔpH) into membrane potential (Δψ) across the SV membrane at the presynaptic terminals. Thus, the proper recruitment of cation/H+ exchanger to SVs is important in determining glutamate quantal size, yet little is known about its localization mechanism. Here, we found that secretory carrier membrane protein 5 (SCAMP5) interacted with the cation/H+ exchanger NHE6, and this interaction regulated NHE6 recruitment to glutamatergic presynaptic terminals. Protein-protein interaction analysis with truncated constructs revealed that the 2/3 loop domain of SCAMP5 is directly associated with the C-terminal region of NHE6. The use of optical imaging and electrophysiological recording showed that small hairpin RNA-mediated knockdown (KD) of SCAMP5 or perturbation of SCAMP5/NHE6 interaction markedly inhibited axonal trafficking and the presynaptic localization of NHE6, leading to hyperacidification of SVs and a reduction in the quantal size of glutamate release. Knockout of NHE6 occluded the effect of SCAMP5 KD without causing additional defects. Together, our results reveal that as a key regulator of axonal trafficking and synaptic localization of NHE6, SCAMP5 could adjust presynaptic strength by regulating quantal size at glutamatergic synapses. Since both proteins are autism candidate genes, the reduced quantal size by interrupting their interaction may underscore synaptic dysfunction observed in autism.
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Abstract
Supplemental Digital Content is Available in the Text. Patients diagnosed with Christianson syndrome have intellectual disability, epilepsy, ataxia, and mutism, as well as hyposensitivity to pain. In this study, we use a mouse model of Christianson syndrome to demonstrate that this pain hyposensitivity is due in part to a decrease in excitability of nociceptors. Children diagnosed with Christianson syndrome (CS), a rare X-linked neurodevelopmental disorder characterized by intellectual disability, epilepsy, ataxia, and mutism, also suffer from hyposensitivity to pain. This places them at risk of sustaining serious injuries that often go unattended. Christianson syndrome is caused by mutations in the alkali cation/proton exchanger SLC9A6/NHE6 that regulates recycling endosomal pH homeostasis and trafficking. Yet, it remains unclear how defects in this transporter lead to altered somatosensory functions. In this study, we validated a Nhe6 knockout (KO) mouse as a model of CS and used it to identify the cellular mechanisms underlying the elevated pain tolerance observed in CS patients. Within the central nervous system, NHE6 immunolabelling is detected in a small percentage of cortical neurons involved in pain processing, including those within the primary somatosensory and the anterior cingulate cortices as well as the periaqueductal gray. Interestingly, it is expressed in a larger percentage of nociceptors. Behaviourally, Nhe6 KO mice have decreased nocifensive responses to acute noxious thermal, mechanical, and chemical (ie, capsaicin) stimuli. The reduced capsaicin sensitivity in the KO mice correlates with a decreased expression of the transient receptor potential channel TRPV1 at the plasma membrane and capsaicin-induced Ca2+ influx in primary cultures of nociceptors. These data indicate that NHE6 is a significant determinant of nociceptor function and pain behaviours, vital sensory processes that are impaired in CS.
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Yalcintepe S, Gurkan H. Novel c.1505_1509dupCTGCC pathogenic variation in a male case with Christianson syndrome. Clin Dysmorphol 2021; 30:36-38. [PMID: 33278113 DOI: 10.1097/mcd.0000000000000358] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Pathogenic variations in the SLC9A6 gene are associated with an X-linked disorder Christianson syndrome characterized by developmental delay, microcephaly, intellectual disability, autistic-like behavior and epilepsy. We identified a novel pathogenic variation in the SLC9A6 gene in a boy with developmental delay and microcephaly. Herein we report the clinical findings of the case diagnosed as Christianson syndrome; his mother was found to carry the same variant.
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Affiliation(s)
- Sinem Yalcintepe
- Department of Medical Genetics, Trakya University Faculty of Medicine, Edirne, Turkey
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Ziats CA, Patterson WG, Friez M. Syndromic Autism Revisited: Review of the Literature and Lessons Learned. Pediatr Neurol 2021; 114:21-25. [PMID: 33189026 DOI: 10.1016/j.pediatrneurol.2020.06.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/01/2020] [Accepted: 06/19/2020] [Indexed: 11/29/2022]
Abstract
Autism spectrum disorder is a neurodevelopmental disorder characterized by deficits in communication, stereotyped behaviors, restricted interests, and impaired social skills. The severity of the neurobehavioral phenotype is variable and historically has been distinguished based on the presence or absence of additional symptoms, termed syndromic and nonsyndromic or idiopathic autism, respectively. However, although the advancement in genetic molecular technologies has brought an increased understanding of the pathophysiology of autism, most of this success has been in the diagnosis of syndromic disease, whereas the etiology of nonsyndromic autism remains less understood. Here we review the common and rare genetic syndromes that feature autism, specifically highlighting deletion and duplication syndromes, chromosomal anomalies, and monogenic disorders. We show that the study of syndromic autism provides insight into the phenotypic and molecular heterogeneity of neurodevelopmental disease and suggests how study of these disorders can be helpful in understanding disease mechanisms implicated in nonsyndromic autism.
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Affiliation(s)
- Catherine A Ziats
- Greenwood Genetic Center, J.C. Self Research Institute, Greenwood, South Carolina.
| | - Wesley G Patterson
- Greenwood Genetic Center, J.C. Self Research Institute, Greenwood, South Carolina
| | - Michael Friez
- Greenwood Genetic Center, J.C. Self Research Institute, Greenwood, South Carolina
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Li T, Tuo B. Pathophysiology of hepatic Na +/H + exchange (Review). Exp Ther Med 2020; 20:1220-1229. [PMID: 32742358 PMCID: PMC7388279 DOI: 10.3892/etm.2020.8888] [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: 09/21/2019] [Accepted: 05/15/2020] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers (NHEs) are a family of membrane proteins that contribute to exchanging one intracellular proton for one extracellular sodium. The family of NHEs consists of nine known members, NHE1-9. Each isoform represents a different gene product that has unique tissue expression, membrane localization, physiological effects, pathological regulation and sensitivity to drug inhibitors. NHE1 was the first to be discovered and is often referred to as the 'housekeeping' isoform of the NHE family. NHEs are not only involved in a variety of physiological processes, including the control of transepithelial Na+ absorption, intracellular pH, cell volume, cell proliferation, migration and apoptosis, but also modulate complex pathological events. Currently, the vast majority of review articles have focused on the role of members of the NHE family in inflammatory bowel disease, intestinal infectious diarrhea and digestive system tumorigenesis, but only a few reviews have discussed the role of NHEs in liver disease. Therefore, the present review described the basic biology of NHEs and highlighted their physiological and pathological effects in the liver.
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Affiliation(s)
- Tingting Li
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, Guizhou 563000, P.R. China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, Guizhou 563000, P.R. China
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Yin J, Chun CA, Zavadenko NN, Pechatnikova NL, Naumova OY, Doddapaneni HV, Hu J, Muzny DM, Schaaf CP, Grigorenko EL. Next Generation Sequencing of 134 Children with Autism Spectrum Disorder and Regression. Genes (Basel) 2020; 11:genes11080853. [PMID: 32722525 PMCID: PMC7463850 DOI: 10.3390/genes11080853] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/14/2020] [Accepted: 07/22/2020] [Indexed: 12/14/2022] Open
Abstract
Approximately 30% of individuals with autism spectrum disorder (ASD) experience developmental regression, the etiology of which remains largely unknown. We performed a complete literature search and identified 47 genes that had been implicated in such cases. We sequenced these genes in a preselected cohort of 134 individuals with regressive autism. In total, 16 variants in 12 genes with evidence supportive of pathogenicity were identified. They were classified as variants of uncertain significance based on ACMG standards and guidelines. Among these were recurring variants in GRIN2A and PLXNB2, variants in genes that were linked to syndromic forms of ASD (GRIN2A, MECP2, CDKL5, SCN1A,PCDH19, UBE3A, and SLC9A6), and variants in the form of oligogenic heterozygosity (EHMT1, SLC9A6, and MFSD8).
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Affiliation(s)
- Jiani Yin
- Molecular and Human Genetics Department, Baylor College of Medicine, Houston, TX 77030, USA; (J.Y.); (C.-A.C.); (C.P.S.)
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX 77030, USA
- Department of Neurology, Center for Autism Research and Treatment, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Chun-An Chun
- Molecular and Human Genetics Department, Baylor College of Medicine, Houston, TX 77030, USA; (J.Y.); (C.-A.C.); (C.P.S.)
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX 77030, USA
| | - Nikolay N. Zavadenko
- Neurology, Neurosurgery and Medical Genetics, Department of Pediatrics, Pirogov Russian National Research Medical University, 117997 Moscow, Russia; (N.N.Z.); (N.L.P.)
| | - Natalia L. Pechatnikova
- Neurology, Neurosurgery and Medical Genetics, Department of Pediatrics, Pirogov Russian National Research Medical University, 117997 Moscow, Russia; (N.N.Z.); (N.L.P.)
| | - Oxana Yu. Naumova
- Texas Institute for Measurement, Evaluation, and Statistics, University of Houston, Houston, TX 77024, USA;
- Vavilov Institute of General Genetics, Russian Academy of Sciences, 119991 Moscow, Russia
- Laboratory of Translational Developmental Sciences, Saint Petersburg State University, 199034 Saint Petersburg, Russia
| | - Harsha V. Doddapaneni
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA; (H.V.D.); (J.H.); (D.M.M.)
| | - Jianhong Hu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA; (H.V.D.); (J.H.); (D.M.M.)
| | - Donna M. Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA; (H.V.D.); (J.H.); (D.M.M.)
| | - Christian P. Schaaf
- Molecular and Human Genetics Department, Baylor College of Medicine, Houston, TX 77030, USA; (J.Y.); (C.-A.C.); (C.P.S.)
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX 77030, USA
- Institute of Human Genetics, Heidelberg University, 69120 Heidelberg, Germany
| | - Elena L. Grigorenko
- Molecular and Human Genetics Department, Baylor College of Medicine, Houston, TX 77030, USA; (J.Y.); (C.-A.C.); (C.P.S.)
- Vavilov Institute of General Genetics, Russian Academy of Sciences, 119991 Moscow, Russia
- Laboratory of Translational Developmental Sciences, Saint Petersburg State University, 199034 Saint Petersburg, Russia
- Correspondence: ; Tel.: +1-713-743-7983
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Ilie A, Boucher A, Park J, Berghuis AM, McKinney RA, Orlowski J. Assorted dysfunctions of endosomal alkali cation/proton exchanger SLC9A6 variants linked to Christianson syndrome. J Biol Chem 2020; 295:7075-7095. [PMID: 32277048 PMCID: PMC7242699 DOI: 10.1074/jbc.ra120.012614] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Genetic screening has identified numerous variants of the endosomal solute carrier family 9 member A6 (SLC9A6)/(Na+,K+)/H+ exchanger 6 (NHE6) gene that cause Christianson syndrome, a debilitating X-linked developmental disorder associated with a range of neurological, somatic, and behavioral symptoms. Many of these variants cause complete loss of NHE6 expression, but how subtler missense substitutions or nonsense mutations that partially truncate its C-terminal cytoplasmic regulatory domain impair NHE6 activity and endosomal function are poorly understood. Here, we describe the molecular and cellular consequences of six unique mutations located in the N-terminal cytoplasmic segment (A9S), the membrane ion translocation domain (L188P and G383D), and the C-terminal regulatory domain (E547*, R568Q, and W570*) of human NHE6 that purportedly cause disease. Using a heterologous NHE6-deficient cell expression system, we show that the biochemical, catalytic, and cellular properties of the A9S and R568Q variants were largely indistinguishable from those of the WT transporter, which obscured their disease significance. By contrast, the L188P, G383D, E547*, and W570* mutants exhibited variable deficiencies in biosynthetic post-translational maturation, membrane sorting, pH homeostasis in recycling endosomes, and cargo trafficking, and they also triggered apoptosis. These findings broaden our understanding of the molecular dysfunctions of distinct NHE6 variants associated with Christianson syndrome.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Jaeok Park
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada
| | | | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
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Ibarluzea N, de la Hoz AB, Villate O, Llano I, Ocio I, Martí I, Guitart M, Gabau E, Andrade F, Gener B, Tejada MI. Targeted Next-Generation Sequencing in Patients with Suggestive X-Linked Intellectual Disability. Genes (Basel) 2020; 11:genes11010051. [PMID: 31906484 PMCID: PMC7017351 DOI: 10.3390/genes11010051] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/19/2019] [Accepted: 12/30/2019] [Indexed: 12/28/2022] Open
Abstract
X-linked intellectual disability (XLID) is known to contribute up to 10% of intellectual disability (ID) in males and could explain the increased ratio of affected males observed in patients with ID. Over the past decade, next-generation sequencing has clearly stimulated the gene discovery process and has become part of the diagnostic procedure. We have performed targeted next-generation sequencing of 82 XLID genes on 61 non-related male patients with suggestive non-syndromic XLID. These patients were initially referred to the molecular genetics laboratory to exclude Fragile X Syndrome. The cohort includes 47 male patients with suggestive X-linked family history of ID meaning that they had half-brothers or maternal cousins or uncles affected; and 14 male patients with ID and affected brothers whose mothers show skewed X-inactivation. Sequencing data analysis identified 17 candidate variants in 16 patients. Seven families could be re-contacted and variant segregation analysis of the respective eight candidate variants was performed: HUWE1, IQSEC2, MAOA, MED12, PHF8, SLC6A8, SLC9A6, and SYN1. Our results show the utility of targeted next-generation sequencing in unravelling the genetic origin of XLID, especially in retrospective cases. Variant segregation and additional studies like RNA sequencing and biochemical assays also helped in re-evaluating and further classifying the genetic variants found.
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Affiliation(s)
- Nekane Ibarluzea
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
| | - Ana Belén de la Hoz
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
| | - Olatz Villate
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, 48903 Barakaldo, Spain
| | - Isabel Llano
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, 48903 Barakaldo, Spain
| | - Intzane Ocio
- Department of Paediatric Neurology, Araba University Hospital, Osakidetza Basque Health Service, 01009 Gasteiz, Spain
| | - Itxaso Martí
- Department of Paediatric Neurology, Donostia University Hospital, Osakidetza Basque Health Service, 20014 Donostia, Spain
| | - Miriam Guitart
- Genetics Laboratory, Paediatric Unit, Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, 08208 Sabadell, Spain
| | - Elisabeth Gabau
- Genetics Laboratory, Paediatric Unit, Parc Taulí Hospital Universitari, Institut d’Investigació i Innovació Parc Taulí I3PT, Universitat Autònoma de Barcelona, 08208 Sabadell, Spain
| | - Fernando Andrade
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
| | - Blanca Gener
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, 48903 Barakaldo, Spain
| | - María-Isabel Tejada
- Biocruces Bizkaia Health Research Institute, 48903 Barakaldo, Spain
- Spanish Consortium for Research on Rare Diseases (CIBERER), 28029 Madrid, Spain
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, 48903 Barakaldo, Spain
- Correspondence:
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Ikeda A, Yamamoto A, Ichikawa K, Tsuyusaki Y, Tsuji M, Iai M, Enomoto Y, Murakami H, Kurosawa K, Miyatake S, Matsumoto N, Goto T. Epilepsy in Christianson syndrome: Two cases of Lennox-Gastaut syndrome and a review of literature. Epilepsy Behav Rep 2019; 13:100349. [PMID: 31879735 PMCID: PMC6920258 DOI: 10.1016/j.ebr.2019.100349] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/19/2019] [Accepted: 12/01/2019] [Indexed: 10/28/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked intellectual disorder caused by mutations in the SLC9A6 gene. Clinical features of CS include an inability to speak, truncal ataxia, postnatal microcephaly, hyperkinesis, and epilepsy. Almost all patients with CS develop drug-resistant epilepsy-its most serious complication. We report two cases of CS with drug-resistant epilpesy associated with the Lennox-Gastaut syndrome (LGS). One patient experienced generalized tonic seizures since 9 months of age with cognitive regression, which evolved to include atonic seizures at the age of 7 years. Electroencephalography (EEG) showed generalized slow spike-wave complexes and generalized paroxysmal fast activity. Seizures remained drug-resistant despite multiple anti-seizure drugs. The second patient experienced generalized tonic seizures since the age of 17 months and arrested development. EEG showed generalized slow spike-wave complexes, with frequent atonic seizures since the age of 6 years. Electrical status epilepticus during slow-wave sleep (ESES) developed at the age of 7 years. Our cases illustrate that CS may cause LGS in addition to other developmental and epileptic encephalopathies of the neonatal and infantile period. We suggest that generalized tonic or tonic-clonic seizures and generalized slow spike-wave complexes in interictal EEG be included as potential electroclinical features of epilepsy in CS.
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Affiliation(s)
- Azusa Ikeda
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Ayako Yamamoto
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Kazushi Ichikawa
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Yu Tsuyusaki
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Megumi Tsuji
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Mizue Iai
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Yumi Enomoto
- Clinical Research Institute, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Hiroaki Murakami
- Division of Medical Genetics, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Kenji Kurosawa
- Division of Medical Genetics, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Tomohide Goto
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
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Functional Assessment In Vivo of the Mouse Homolog of the Human Ala-9-Ser NHE6 Variant. eNeuro 2019; 6:ENEURO.0046-19.2019. [PMID: 31676550 PMCID: PMC6893231 DOI: 10.1523/eneuro.0046-19.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 10/24/2019] [Accepted: 10/30/2019] [Indexed: 11/21/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked neurogenetic disorder resulting from loss-of-function (LoF) mutations in SLC9A6, which encodes the endosomal Na+/H+ exchanger 6 (NHE6). NHE6 regulates proton efflux from endosomes and, thus, participates in regulating cargo processing and trafficking. LoF mutations in NHE6 cause aberrant acidification of endosomes. While CS arises in males generally due to clear LoF mutations, other potentially hypomorphic variants have emerged, yet most of these variants have not been evaluated for functional effects, particularly in vivo Here we characterize an SLC9A6 variant that has been previously reported in patients, yet now also appears in exome datasets of largely control individuals-c.25G>T, p.A9S. By heterologous expression in cell lines, we show that human NHE6A9S is expressed and localizes in a manner comparable to control NHE6. By genome editing, we generated the equivalent NHE6 mutation in mouse-p.A11S-and determined that male NHE6A11S mice have normal brain size at 6 months of age and do not show cerebellar degeneration or defective neuronal arborization. Neurons from male NHE6A11S mice also did not demonstrate an abnormality in intraendosomal pH compared with controls. These findings are in contrast to findings in NHE6-null mice previously reported and indicate that the NHE6A11S variant functions at a level equivalent to control NHE6 for many of the assays performed. These data stand in support of the population genetic data, which are also evaluated here, indicating that the A9S variant is unlikely to confer disease susceptibility with high penetrance.
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Kerner-Rossi M, Gulinello M, Walkley S, Dobrenis K. Pathobiology of Christianson syndrome: Linking disrupted endosomal-lysosomal function with intellectual disability and sensory impairments. Neurobiol Learn Mem 2019; 165:106867. [PMID: 29772390 PMCID: PMC6235725 DOI: 10.1016/j.nlm.2018.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 05/04/2018] [Accepted: 05/12/2018] [Indexed: 11/18/2022]
Abstract
Christianson syndrome (CS) is a recently described rare neurogenetic disorder presenting early in life with a broad range of neurological symptoms, including severe intellectual disability with nonverbal status, hyperactivity, epilepsy, and progressive ataxia due to cerebellar atrophy. CS is due to loss-of-function mutations in SLC9A6, encoding NHE6, a sodium-hydrogen exchanger involved in the regulation of early endosomal pH. Here we review what is currently known about the neuropathogenesis of CS, based on insights from experimental models, which to date have focused on mechanisms that affect the CNS, specifically the brain. In addition, parental reports of sensory disturbances in their children with CS, including an apparent insensitivity to pain, led us to explore sensory function and related neuropathology in Slc9a6 KO mice. We present new data showing sensory deficits in Slc9a6 KO mice, which had reduced behavioral responses to noxious thermal and mechanical stimuli (Hargreaves and Von Frey assays, respectively) compared to wild type (WT) littermates. Immunohistochemical and ultrastructural analysis of the spinal cord and peripheral nervous system revealed intracellular accumulation of the glycosphingolipid GM2 ganglioside in KO but not WT mice. This cellular storage phenotype was most abundant in neurons of lamina I-II of the dorsal horn, a major relay site in the processing of painful stimuli. Spinal cords of KO mice also exhibited changes in astroglial and microglial populations throughout the gray matter suggestive of a neuroinflammatory process. Our findings establish the Slc9a6 KO mouse as a relevant tool for studying the sensory deficits in CS, and highlight selective vulnerabilities in relevant cell populations that may contribute to this phenotype. How NHE6 loss of function leads to such a multifaceted neurological syndrome is still undefined, and it is likely that NHE6 is involved with many cellular processes critical to normal nervous system development and function. In addition, the sensory issues exhibited by Slc9a6 KO mice, in combination with our neuropathological findings, are consistent with NHE6 loss of function impacting the entire nervous system. Sensory dysfunction in intellectually disabled individuals is challenging to assess and may impair patient safety and quality of life. Further mechanistic studies of the neurological impairments underlying CS and other genetic intellectual disability disorders must also take into account mechanisms affecting broader nervous system function in order to understand the full range of associated disabilities.
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Affiliation(s)
- Mallory Kerner-Rossi
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Maria Gulinello
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA; IDDRC Behavioral Core Facility, Neuroscience Department, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Steven Walkley
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Kostantin Dobrenis
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Khayat W, Hackett A, Shaw M, Ilie A, Dudding-Byth T, Kalscheuer VM, Christie L, Corbett MA, Juusola J, Friend KL, Kirmse BM, Gecz J, Field M, Orlowski J. A recurrent missense variant in SLC9A7 causes nonsyndromic X-linked intellectual disability with alteration of Golgi acidification and aberrant glycosylation. Hum Mol Genet 2019; 28:598-614. [PMID: 30335141 DOI: 10.1093/hmg/ddy371] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 10/12/2018] [Indexed: 11/13/2022] Open
Abstract
We report two unrelated families with multigenerational nonsyndromic intellectual disability (ID) segregating with a recurrent de novo missense variant (c.1543C>T:p.Leu515Phe) in the alkali cation/proton exchanger gene SLC9A7 (also commonly referred to as NHE7). SLC9A7 is located on human X chromosome at Xp11.3 and has not yet been associated with a human phenotype. The gene is widely transcribed, but especially abundant in brain, skeletal muscle and various secretory tissues. Within cells, SLC9A7 resides in the Golgi apparatus, with prominent enrichment in the trans-Golgi network (TGN) and post-Golgi vesicles. In transfected Chinese hamster ovary AP-1 cells, the Leu515Phe mutant protein was correctly targeted to the TGN/post-Golgi vesicles, but its N-linked oligosaccharide maturation as well as that of a co-transfected secretory membrane glycoprotein, vesicular stomatitis virus G (VSVG) glycoprotein, was reduced compared to cells co-expressing SLC9A7 wild-type and VSVG. This correlated with alkalinization of the TGN/post-Golgi compartments, suggestive of a gain-of-function. Membrane trafficking of glycosylation-deficient Leu515Phe and co-transfected VSVG to the cell surface, however, was relatively unaffected. Mass spectrometry analysis of patient sera also revealed an abnormal N-glycosylation profile for transferrin, a clinical diagnostic marker for congenital disorders of glycosylation. These data implicate a crucial role for SLC9A7 in the regulation of TGN/post-Golgi pH homeostasis and glycosylation of exported cargo, which may underlie the cellular pathophysiology and neurodevelopmental deficits associated with this particular nonsyndromic form of X-linked ID.
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Affiliation(s)
- Wujood Khayat
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Anna Hackett
- Genetics of Learning Disability Service, Hunter Genetics, Waratah, NSW, Australia
| | - Marie Shaw
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia
| | - Alina Ilie
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Tracy Dudding-Byth
- Genetics of Learning Disability Service, Hunter Genetics, Waratah, NSW, Australia
| | - Vera M Kalscheuer
- Research Group Development and Disease, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Louise Christie
- Genetics of Learning Disability Service, Hunter Genetics, Waratah, NSW, Australia
| | - Mark A Corbett
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia
| | | | - Kathryn L Friend
- Genetics and Molecular Pathology, SA Pathology, Adelaide, SA, Australia
| | - Brian M Kirmse
- Department of Pediatrics, Division of Medical Genetics, University of Mississippi Medical Center, Jackson, MS, USA
| | - Jozef Gecz
- Adelaide Medical School and Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia.,South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Michael Field
- Genetics of Learning Disability Service, Hunter Genetics, Waratah, NSW, Australia
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Quebec, Canada
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Chukwurah E, Osmundsen A, Davis SW, Lizarraga SB. All Together Now: Modeling the Interaction of Neural With Non-neural Systems Using Organoid Models. Front Neurosci 2019; 13:582. [PMID: 31293366 PMCID: PMC6598414 DOI: 10.3389/fnins.2019.00582] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 05/22/2019] [Indexed: 12/27/2022] Open
Abstract
The complex development of the human nervous system has been traditionally studied using a combination of animal models, human post-mortem brain tissue, and human genetics studies. However, there has been a lack of experimental human cellular models that would allow for a more precise elucidation of the intricate dynamics of early human brain development. The development of stem cell technologies, both embryonic and induced pluripotent stem cells (iPSCs), has given neuroscientists access to the previously inaccessible early stages of human brain development. In particular, the recent development of three-dimensional culturing methodologies provides a platform to study the differentiation of stem cells in both normal development and disease states in a more in vivo like context. Three-dimensional neural models or cerebral organoids possess an innate advantage over two-dimensional neural cultures as they can recapitulate tissue organization and cell type diversity that resemble the developing brain. Brain organoids also provide the exciting opportunity to model the integration of different brain regions in vitro. Furthermore, recent advances in the differentiation of non-neuronal tissue from stem cells provides the opportunity to study the interaction between the developing nervous system and other non-neuronal systems that impact neuronal function. In this review, we discuss the potential and limitations of the organoid system to study in vitro neurological diseases that arise in the neuroendocrine and the enteric nervous system or from interactions with the immune system.
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Affiliation(s)
- Evelyn Chukwurah
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
- Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC, United States
| | - Allison Osmundsen
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
- Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC, United States
| | - Shannon W. Davis
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
- Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC, United States
| | - Sofia B. Lizarraga
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
- Center for Childhood Neurotherapeutics, University of South Carolina, Columbia, SC, United States
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A Christianson syndrome-linked deletion mutation (Δ287ES288) in SLC9A6 impairs hippocampal neuronal plasticity. Neurobiol Dis 2019; 130:104490. [PMID: 31175985 DOI: 10.1016/j.nbd.2019.104490] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/25/2019] [Accepted: 06/04/2019] [Indexed: 02/07/2023] Open
Abstract
Christianson Syndrome is a rare but increasingly diagnosed X-linked intellectual disability disorder that arises from mutations in SLC9A6/NHE6, a pH-regulating transporter that localizes to early and recycling endosomes. We have recently reported that one of the originally identified disease-causing mutations in NHE6 (p.E287-S288del, or ΔES) resulted in a loss of its pH regulatory function. However, the impact of this mutation upon neuronal synapse formation and plasticity is unknown. Here, we investigate the consequences of the ΔES mutant upon mouse hippocampal pyramidal neurons by expressing a fluorescently-labeled ΔES NHE6 construct into primary hippocampal neurons. Neurons expressing the ΔES mutant showed significant reductions in mature dendritic spine density with a concurrent increase in immature filopodia. Furthermore, compared to wild-type (WT), ΔES-containing endosomes are redirected away from early and recycling endosomes toward lysosomes. In parallel, the ΔES mutant reduced the trafficking of glutamatergic AMPA receptors to excitatory synapses and increased their accumulation within lysosomes for potential degradation. Upon long-term potentiation (LTP), neurons expressing ΔES failed to undergo significant structural and functional changes as observed in controls and WT transfectants. Interestingly, synapse density and LTP-induced synaptic remodeling in ΔES-expressing neurons were partially restored by bafilomycin, a vesicular alkalinisation agent, or by leupeptin, an inhibitor of lysosomal proteolytic degradation. Overall, our results demonstrate that the ∆ES mutation attenuates synapse density and structural and functional plasticity in hippocampal neurons. These deficits may be partially due to the mistargeting of AMPA receptors and other cargos to lysosomes, thereby preventing their trafficking during synaptic remodeling. This mechanism may contribute to the cognitive learning deficits observed in patients with Christianson Syndrome and suggests a potential therapeutic strategy for treatment.
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A novel splicing mutation in SLC9A6 in a boy with Christianson syndrome. Hum Genome Var 2019; 6:15. [PMID: 30937176 PMCID: PMC6434044 DOI: 10.1038/s41439-019-0046-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 01/10/2019] [Accepted: 02/18/2019] [Indexed: 12/01/2022] Open
Abstract
A loss of function mutation in SLC9A6 (Xq26.3) is responsible for Christianson syndrome in males. We identified a novel splicing mutation (NM_006359.2:c.1141-8C>A) of SLC9A6 in a seven-year-old boy with microcephaly, severe developmental delay, and intractable epilepsy. Functional analysis found multiple aberrant transcripts, none of which maintained the canonical open reading frame. Computer prediction tools, however, failed to detect all of the aberrant transcripts.
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Pescosolido MF, Kavanaugh BC, Pochet N, Schmidt M, Jerskey BA, Rogg JM, De Jager PL, Young-Pearse TL, Liu JS, Morrow EM. Complex Neurological Phenotype in Female Carriers of NHE6 Mutations. MOLECULAR NEUROPSYCHIATRY 2019; 5:98-108. [PMID: 31192222 DOI: 10.1159/000496341] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022]
Abstract
Mutations in NHE6 (also termed SLC9A6) cause the X-linked neurological disorder Christianson syndrome (CS) in males. The purpose of this study was to examine the phenotypic spectrum of female carriers of NHE6 mutations. Twenty female carriers from 9 pedigrees were enrolled, ranging from approximately age 2 to 65. A subset of female carriers was assessed using standardized neuropsychological measures. Also, the association of NHE6 expression with markers of brain age was evaluated using 740 participants in the Religious Orders Study (ROS) and Rush Memory and Aging Project (MAP). A majority, but not all, female carriers demonstrated a deficit in at least one neurocognitive domain (85%). A recognizable neuropsychological profile emerged, revealing impairments in visuospatial function, attention, and executive function. Common neuropsychiatric diagnoses included: intellectual disability/developmental delay (20%), learning difficulties (31%), speech/language delays (30%), and attention-deficit/hyperactivity disorder (20%). Notable neurological diagnoses in aging CS female carriers include corticobasal degeneration and atypical parkinsonism. In postmortem brains from the ROS/MAP dataset of normal and pathological aging, decreased NHE6 expression was correlated with greater tau deposition. Our study provides an examination of the phenotypic range in female carriers of NHE6 mutations. The findings indicate that NHE6-related disease in females represents a new neurogenetic condition.
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Affiliation(s)
- Matthew F Pescosolido
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Brian C Kavanaugh
- Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Nathalie Pochet
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA.,Cell Circuits Program, Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, Massachusetts, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Beth A Jerskey
- Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA
| | - Jeffrey M Rogg
- Department of Diagnostic Imaging, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Philip L De Jager
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA.,Cell Circuits Program, Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, Massachusetts, USA
| | - Tracy L Young-Pearse
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Judy S Liu
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Department of Neurology, Rhode Island Hospital, Providence, Rhode Island, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
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A potential gain-of-function variant of SLC9A6 leads to endosomal alkalinization and neuronal atrophy associated with Christianson Syndrome. Neurobiol Dis 2019; 121:187-204. [DOI: 10.1016/j.nbd.2018.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 09/18/2018] [Accepted: 10/03/2018] [Indexed: 11/24/2022] Open
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Identification of candidate gene FAM183A and novel pathogenic variants in known genes: High genetic heterogeneity for autosomal recessive intellectual disability. PLoS One 2018; 13:e0208324. [PMID: 30500859 PMCID: PMC6267965 DOI: 10.1371/journal.pone.0208324] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 11/15/2018] [Indexed: 11/19/2022] Open
Abstract
The etiology of intellectual disability (ID) is heterogeneous including a variety of genetic and environmental causes. Historically, most research has not focused on autosomal recessive ID (ARID), which is a significant cause of ID, particularly in areas where parental consanguinity is common. Identification of genetic causes allows for precision diagnosis and improved genetic counseling. We performed whole exome sequencing to 21 Turkish families, seven multiplex and 14 simplex, with nonsyndromic ID. Based on the presence of multiple affected siblings born to unaffected parents and/or shared ancestry, we consider all families as ARID. We revealed the underlying causative variants in seven families in MCPH1 (c.427dupA, p.T143Nfs*5), WDR62 (c.3406C>T, p.R1136*), ASPM (c.5219_5225delGAGGATA, p.R1740Tfs*7), RARS (c.1588A>G, p.T530A), CC2D1A (c.811delG, p.A271Pfs*30), TUSC3 (c.793C>T, p.Q265*) and ZNF335 (c.808C>T, p.R270C and c.3715C>A, p.Q1239K) previously linked with ARID. Besides ARID genes, in one family, affected male siblings were hemizygous for PQBP1 (c.459_462delAGAG, p.R153Sfs*41) and in one family the proband was female and heterozygous for X-chromosomal SLC9A6 (c.1631+1G>A) variant. Each of these variants, except for those in MCPH1 and PQBP1, have not been previously published. Additionally in one family, two affected children were homozygous for the c.377G>A (p.W126*) variant in the FAM183A, a gene not previously associated with ARID. No causative variants were found in the remaining 11 families. A wide variety of variants explain half of families with ARID. FAM183A is a promising novel candidate gene for ARID.
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Mathieu ML, de Bellescize J, Till M, Flurin V, Labalme A, Chatron N, Sanlaville D, Chemaly N, des Portes V, Ostrowsky K, Arzimanoglou A, Lesca G. Electrical status epilepticus in sleep, a constitutive feature of Christianson syndrome? Eur J Paediatr Neurol 2018; 22:1124-1132. [PMID: 30126759 DOI: 10.1016/j.ejpn.2018.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 06/25/2018] [Accepted: 07/16/2018] [Indexed: 10/28/2022]
Abstract
Christianson syndrome (CS) is a X-linked neurodevelopmental disorder, including severe intellectual disability (ID), progressive microcephaly, ataxia, autistic behaviour (ASD), near absent speech, and epilepsy. Electrical status epilepticus in sleep (ESES) has been reported in two patients. We describe five male patients from three unrelated families with Christianson syndrome caused by a pathogenic nucleotide variation or a copy-number variation involving SLC9A6. ESES was present in three out of the five patients in the critical age window between 4 and 8 years. All patients presented with severe intellectual disability, autistic features, and hyperactivity. Epilepsy onset occurred within the first two years of life. Seizures were of various types. In the two boys with a 20-years follow-up, epilepsy was drug-resistant during childhood, and became less active in early adolescence. Psychomotor regression was noted in two patients presenting with ESES. It was difficult to assess to what extent ESES could have contributed to the pathophysiological process, leading to regression of the already very limited communication skills. The two published case reports and our observation suggests that ESES could be a constitutive feature of Christianson syndrome, as it has already been shown for other Mendelian epileptic disorders, such as GRIN2A and CNKSR2-related developmental epileptic encephalopathies. Sleep EEG should be performed in patients with Christianson syndrome between 4 and 8 years of age. ESES occurring in the context of ID, ASD and severe speech delay, could be helpful to make a diagnosis of CS.
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Affiliation(s)
- Marie-Laure Mathieu
- Neuropaediatrics Department, Femme Mère Enfant Hospital, Lyon, France; Claude Bernard Lyon 1 University, Lyon, France
| | - Julitta de Bellescize
- Department of Paediatric Clinical Epileptology, Sleep Disorders and Functional Neurology, Member of the European Reference Network EpiCARE, Hospices Civils de Lyon, Lyon, France
| | - Marianne Till
- Department of Medical Genetics, Lyon University Hospital, Lyon, France
| | - Vincent Flurin
- Department of Paediatric Intensive Care, Le Mans Hospital, Le Mans, France
| | - Audrey Labalme
- Department of Medical Genetics, Lyon University Hospital, Lyon, France
| | - Nicolas Chatron
- Department of Medical Genetics, Lyon University Hospital, Lyon, France; Claude Bernard Lyon 1 University, Lyon, France; INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Centre (CRNL), Lyon, France
| | - Damien Sanlaville
- Department of Medical Genetics, Lyon University Hospital, Lyon, France; Claude Bernard Lyon 1 University, Lyon, France; INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Centre (CRNL), Lyon, France
| | - Nicole Chemaly
- Reference Centre for Rare Epilepsies, APHP, Necker-Enfants Malades Hospital, Imagine Institute, Paris, France; INSERM U1129, Paris, France; Paris Descartes University, CEA, Gif sur Yvette, France
| | - Vincent des Portes
- Neuropaediatrics Department, Femme Mère Enfant Hospital, Lyon, France; Claude Bernard Lyon 1 University, Lyon, France
| | - Karine Ostrowsky
- Department of Paediatric Clinical Epileptology, Sleep Disorders and Functional Neurology, Member of the European Reference Network EpiCARE, Hospices Civils de Lyon, Lyon, France
| | - Alexis Arzimanoglou
- Department of Paediatric Clinical Epileptology, Sleep Disorders and Functional Neurology, Member of the European Reference Network EpiCARE, Hospices Civils de Lyon, Lyon, France; DYCOG Team, Lyon Neuroscience Research Centre (CRNL), INSERM U1028, CNRS UMR 5292, Lyon, France
| | - Gaëtan Lesca
- Department of Medical Genetics, Lyon University Hospital, Lyon, France; Claude Bernard Lyon 1 University, Lyon, France; INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Centre (CRNL), Lyon, France.
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Amyloid clearance defect in ApoE4 astrocytes is reversed by epigenetic correction of endosomal pH. Proc Natl Acad Sci U S A 2018; 115:E6640-E6649. [PMID: 29946028 DOI: 10.1073/pnas.1801612115] [Citation(s) in RCA: 114] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Endosomes have emerged as a central hub and pathogenic driver of Alzheimer's disease (AD). The earliest brain cytopathology in neurodegeneration, occurring decades before amyloid plaques and cognitive decline, is an expansion in the size and number of endosomal compartments. The strongest genetic risk factor for sporadic AD is the ε4 allele of Apolipoprotein E (ApoE4). Previous studies have shown that ApoE4 potentiates presymptomatic endosomal dysfunction and defective endocytic clearance of amyloid beta (Aβ), although how these two pathways are linked at a cellular and mechanistic level has been unclear. Here, we show that aberrant endosomal acidification in ApoE4 astrocytes traps the low-density lipoprotein receptor-related protein (LRP1) within intracellular compartments, leading to loss of surface expression and Aβ clearance. Pathological endosome acidification is caused by ε4 risk allele-selective down-regulation of the Na+/H+ exchanger isoform NHE6, which functions as a critical leak pathway for endosomal protons. In vivo, the NHE6 knockout (NHE6KO) mouse model showed elevated Aβ in the brain, consistent with a causal effect. Increased nuclear translocation of histone deacetylase 4 (HDAC4) in ApoE4 astrocytes, compared with the nonpathogenic ApoE3 allele, suggested a mechanistic basis for transcriptional down-regulation of NHE6. HDAC inhibitors that restored NHE6 expression normalized ApoE4-specific defects in endosomal pH, LRP1 trafficking, and amyloid clearance. Thus, NHE6 is a downstream effector of ApoE4 and emerges as a promising therapeutic target in AD. These observations have prognostic implications for patients who have Christianson syndrome with loss of function mutations in NHE6 and exhibit prominent glial pathology and progressive hallmarks of neurodegeneration.
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45
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Lesca G. Aspetti genetici delle epilessie. Neurologia 2018. [DOI: 10.1016/s1634-7072(18)41286-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Weitensteiner V, Zhang R, Bungenberg J, Marks M, Gehlen J, Ralser DJ, Hilger AC, Sharma A, Schumacher J, Gembruch U, Merz WM, Becker A, Altmüller J, Thiele H, Herrmann BG, Odermatt B, Ludwig M, Reutter H. Exome sequencing in syndromic brain malformations identifies novel mutations in ACTB, and SLC9A6, and suggests BAZ1A as a new candidate gene. Birth Defects Res 2018; 110:587-597. [PMID: 29388391 DOI: 10.1002/bdr2.1200] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/07/2017] [Accepted: 01/06/2018] [Indexed: 02/01/2023]
Abstract
BACKGROUND Syndromic brain malformations comprise a large group of anomalies with a birth prevalence of about 1 in 1,000 live births. Their etiological factors remain largely unknown. To identify causative mutations, we used whole-exome sequencing (WES) in aborted fetuses and children with syndromic brain malformations in which chromosomal microarray analysis was previously unremarkable. METHODS WES analysis was applied in eight case-parent trios, six aborted fetuses, and two children. RESULTS WES identified a novel de novo mutation (p.Gly268Arg) in ACTB (Baraitser-Winter syndrome-1), a homozygous stop mutation (p.R2442*) in ASPM (primary microcephaly type 5), and a novel hemizygous X-chromosomal mutation (p.I250V) in SLC9A6 (X-linked syndromic mentaly retardation, Christianson type). Furthermore, WES identified a de novo mutation (p.Arg1093Gln) in BAZ1A. This mutation was previously reported in only one allele in 121.362 alleles tested (dbSNP build 147). BAZ1A has been associated with neurodevelopmental impairment and dysregulation of several pathways including vitamin D metabolism. Here, serum vitamin-D (25-(OH)D) levels were insufficient and gene expression comparison between the child and her parents identified 27 differentially expressed genes. Of note, 10 out of these 27 genes are associated to cytoskeleton, integrin and synaptic related pathways, pinpointing to the relevance of BAZ1A in neural development. In situ hybridization in mouse embryos between E10.5 and E13.5 detected Baz1a expression in the central and peripheral nervous system. CONCLUSION In syndromic brain malformations, WES is likely to identify causative mutations when chromosomal microarray analysis is unremarkable. Our findings suggest BAZ1A as a possible new candidate gene.
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Affiliation(s)
- Valerie Weitensteiner
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany
| | - Rong Zhang
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany.,Department of Genomics-Life & Brain Center, Bonn, Germany
| | | | - Matthias Marks
- Department of Developmental Genetics, Max-Planck-Institute for Molecular Genetics, Berlin, Germany
| | - Jan Gehlen
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany.,Department of Genomics-Life & Brain Center, Bonn, Germany
| | - Damian J Ralser
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany
| | - Alina C Hilger
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany.,Department of Pediatrics, University of Bonn, Bonn, Germany
| | - Amit Sharma
- Department of Neurology, University Clinic Bonn, Bonn, Germany
| | - Johannes Schumacher
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany.,Department of Genomics-Life & Brain Center, Bonn, Germany
| | - Ulrich Gembruch
- Department of Obstetrics and Prenatal Medicine, University of Bonn, Bonn, Germany
| | - Waltraut M Merz
- Department of Obstetrics and Prenatal Medicine, University of Bonn, Bonn, Germany
| | - Albert Becker
- Department of Neuropathology, University of Bonn, Bonn, Germany
| | - Janine Altmüller
- Cologne Center for Genomics, University of Cologne, Cologne, Germany.,Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Holger Thiele
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Bernhard G Herrmann
- Department of Developmental Genetics, Max-Planck-Institute for Molecular Genetics, Berlin, Germany
| | | | - Michael Ludwig
- Department of Clinical Chemistry and Clinical Pharmacology, University of Bonn, Bonn, Germany
| | - Heiko Reutter
- Institute of Human Genetics, University of Bonn School of Medicine and University Hospital of Bonn, Bonn, Germany.,Department of Genomics-Life & Brain Center, Bonn, Germany.,Department of Neonatology and Pediatric Intensive Care, Children's Hospital, University of Bonn, Bonn, Germany
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Thurm A, Powell EM, Neul JL, Wagner A, Zwaigenbaum L. Loss of skills and onset patterns in neurodevelopmental disorders: Understanding the neurobiological mechanisms. Autism Res 2018; 11:212-222. [PMID: 29226600 PMCID: PMC5825269 DOI: 10.1002/aur.1903] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 11/19/2017] [Accepted: 11/25/2017] [Indexed: 12/15/2022]
Abstract
Patterns of onset in Autism Spectrum Disorder, including a pattern that includes loss of previously acquired skills, have been identified since the first reports of the disorder. However, attempts to study such "regression" have been limited to clinical studies, that until recently mostly involved retrospective reports. The current report reflects discussion that occurred at an NIMH convened meeting in 2016 with the purpose of bridging clinical autism research with basic and translational work in this area. This summary describes the state of the field with respect to clinical studies, describing gaps in knowledge based on limited methods and prospective data collected. Biological mechanisms that have been shown to account for regression early in development in specific conditions are discussed, as well as potential mechanisms that have not yet been explored. Suggestions include use of model systems during the developmental period and cutting-edge methods, including non-invasive imaging that may afford opportunities for a better understanding of the neurobiological pathways that result in loss of previously-attained skills. Autism Res 2018, 11: 212-222. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY Loss of previously acquired skills, or regression, has been reported in Autism Spectrum Disorder since Kanner's reports in the 1950's. The current report reflects discussion from an NIMH convened meeting in 2016 with the purpose of bridging clinical autism research with basic and translational work in this area. This summary describes the state of the field regarding clinical studies and suggests use of model systems during the developmental period and cutting-edge methods, for a better understanding of the neurobiological pathways that result in loss of previously-attained skills.
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Affiliation(s)
- Audrey Thurm
- Office of the Clinical Director, National Institute of Mental Health, National Institute of Health, Bethesda, Maryland, USA
| | - Elizabeth M. Powell
- Division of Neuroscience and Behavior, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Jeffrey L. Neul
- Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ann Wagner
- Division of Translational Research, National Institute of Mental Health, National Institute of Health, Bethesda, Maryland, USA
| | - Lonnie Zwaigenbaum
- Autism Research Center, Glenrose Rehabilitation Hospital, Edmonton, Alberta, Canada
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Mixed Neurodevelopmental and Neurodegenerative Pathology in Nhe6-Null Mouse Model of Christianson Syndrome. eNeuro 2018; 4:eN-NWR-0388-17. [PMID: 29349289 PMCID: PMC5771691 DOI: 10.1523/eneuro.0388-17.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/12/2017] [Accepted: 12/17/2017] [Indexed: 12/20/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked disorder resulting from loss-of-function mutations in SLC9A6, which encodes the endosomal Na+/H+ exchanger 6 (NHE6). Symptoms include early developmental delay, seizures, intellectual disability, nonverbal status, autistic features, postnatal microcephaly, and progressive ataxia. Neuronal development is impaired in CS, involving defects in neuronal arborization and synaptogenesis, likely underlying diminished brain growth postnatally. In addition to neurodevelopmental defects, some reports have supported neurodegenerative pathology in CS with age. The objective of this study was to determine the nature of progressive changes in the postnatal brain in Nhe6-null mice. We examined the trajectories of brain growth and atrophy in mutant mice from birth until very old age (2 yr). We report trajectories of volume changes in the mutant that likely reflect both brain undergrowth as well as tissue loss. Reductions in volume are first apparent at 2 mo, particularly in the cerebellum, which demonstrates progressive loss of Purkinje cells (PCs). We report PC loss in two distinct Nhe6-null mouse models. More widespread reductions in tissue volumes, namely, in the hippocampus, striatum, and cortex, become apparent after 2 mo, largely reflecting delays in growth with more limited tissue losses with aging. Also, we identify pronounced glial responses, particularly in major fiber tracts such as the corpus callosum, where the density of activated astrocytes and microglia are substantially increased. The prominence of the glial response in axonal tracts suggests a primary axonopathy. Importantly, therefore, our data support both neurodevelopmental and degenerative mechanisms in the pathobiology of CS.
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Abstract
PURPOSE OF REVIEW Studies investigating postnatal brain growth disorders inform the biology underlying the development of human brain circuitry. This research is becoming increasingly important for the diagnosis and treatment of childhood neurodevelopmental disorders, including autism and related disorders. Here, we review recent research on typical and abnormal postnatal brain growth and examine potential biological mechanisms. RECENT FINDINGS Clinically, brain growth disorders are heralded by diverging head size for a given age and sex, but are more precisely characterized by brain imaging, post-mortem analysis, and animal model studies. Recent neuroimaging and molecular biological studies on postnatal brain growth disorders have broadened our view of both typical and pathological postnatal neurodevelopment. Correlating gene and protein function with brain growth trajectories uncovers postnatal biological mechanisms, including neuronal arborization, synaptogenesis and pruning, and gliogenesis and myelination. Recent investigations of childhood neurodevelopmental and neurodegenerative disorders highlight the underlying genetic programming and experience-dependent remodeling of neural circuitry. SUMMARY To understand typical and abnormal postnatal brain development, clinicians and researchers should characterize brain growth trajectories in the context of neurogenetic syndromes. Understanding mechanisms and trajectories of postnatal brain growth will aid in differentiating, diagnosing, and potentially treating neurodevelopmental disorders.
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Abstract
X-linked cerebellar ataxias (XLCA) are an expanding group of genetically heterogeneous and clinically variable conditions characterized by cerebellar dysgenesis (hypoplasia, atrophy, or dysplasia) caused by gene mutations or genomic imbalances on the X chromosome. The neurologic features of XLCA include hypotonia, developmental delay, intellectual disability, ataxia, and other cerebellar signs. Normal cognitive development has also been reported. Cerebellar defects may be isolated or associated with other brain malformations or extraneurologic involvement. More than 20 genes on the X chromosome, mainly encoding for proteins involved in brain development and synaptic function that have been constantly or occasionally associated with a pathologic cerebellar phenotype, and several families with X-linked inheritance have been reported. Given the excess of males with ataxia, this group of conditions is probably underestimated and families of patients with neuroradiologic and clinical evidence of a cerebellar disorder should be counseled for high risk of X-linked inheritance.
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Affiliation(s)
- Ginevra Zanni
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesu' Children's Research Hospital, Rome, Italy.
| | - Enrico Bertini
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesu' Children's Research Hospital, Rome, Italy
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