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He H, Li X, Guzman GA, Bungert-Plümke S, Franzen A, Lin X, Zhu H, Peng G, Zhang H, Yu Y, Sun S, Huang Z, Zhai Q, Chen Z, Peng J, Guzman RE. Expanding the genetic and phenotypic relevance of CLCN4 variants in neurodevelopmental condition: 13 new patients. J Neurol 2024:10.1007/s00415-024-12383-4. [PMID: 38758281 DOI: 10.1007/s00415-024-12383-4] [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: 02/24/2024] [Revised: 04/02/2024] [Accepted: 04/09/2024] [Indexed: 05/18/2024]
Abstract
OBJECTIVES CLCN4 variations have recently been identified as a genetic cause of X-linked neurodevelopmental disorders. This study aims to broaden the phenotypic spectrum of CLCN4-related condition and correlate it with functional consequences of CLCN4 variants. METHODS We described 13 individuals with CLCN4-related neurodevelopmental disorder. We analyzed the functional consequence of the unreported variants using heterologous expression, biochemistry, confocal fluorescent microscopy, patch-clamp electrophysiology, and minigene splicing assay. RESULTS We identified five novel (p.R41W, p.L348V, p.G480R, p.R603W, c.1576 + 5G > A) and three known (p.T203I, p.V275M, p.A555V) pathogenic CLCN4 variants in 13 Chinese patients. The p.V275M variant is found at high frequency and seen in four unrelated individuals. All had global developmental delay (GDD)/intellectual disability (ID). Seizures were present in eight individuals, and 62.5% of them developed refractory epilepsy. Five individuals without seizures showed moderate to severe GDD/ID. Developmental delay precedes seizure onset in most patients. The variants p.R41W, p.L348V, and p.R603W compromise the anion/exchange function of ClC-4. p.R41W partially impairs ClC-3/ClC-4 association. p.G480R reduces ClC-4 expression levels and impairs the heterodimerization with ClC-3. The c.1576 + 5G > A variant causes 22 bp deletion of exon 10. CONCLUSIONS We further define and broaden the clinical and mutational spectrum of CLCN4-related neurodevelopmental conditions. The p.V275M variant may be a potential hotspot CLCN4 variant in Chinese patients. The five novel variants cause loss of function of ClC-4. Transport dysfunction, protein instability, intracellular trafficking defect, or failure of ClC-4 to oligomerize may contribute to the pathophysiological events leading to CLCN4-related neurodevelopmental disorder.
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Affiliation(s)
- Hailan He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - Xinyi Li
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - G A Guzman
- Institute of Biological Information Processing (IBI-7), Structural Biochemistry, Jülich Research Center, Jülich, Germany
| | - Stefanie Bungert-Plümke
- Institute of Biological Information Processing (IBI-1), Molecular and Cell Physiology, Jülich Research Center, Jülich, Germany
| | - Arne Franzen
- Institute of Biological Information Processing (IBI-1), Molecular and Cell Physiology, Jülich Research Center, Jülich, Germany
| | - XueQin Lin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - Hongmin Zhu
- Department of Rehabilitation, Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Guilan Peng
- Department of Neurology, Xiamen Maternal and Child Health Care Hospital, Xiamen, China
| | - Hongwei Zhang
- Epilepsy Center, Children's Hospital Affiliated to Shandong University, Jinan, China
| | - Yonglin Yu
- Department of Rehabilitation, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Suzhen Sun
- Department of Pediatric Neurology, Hebei Children's Hospital, Hebei Medical University, Shijiazhuang, China
| | - Zhongqin Huang
- Department of Neurology, Xiamen Maternal and Child Health Care Hospital, Xiamen, China
| | - Qiongxiang Zhai
- Department of Pediatrics, Guangdong Provincial People's Hospital, Guangzhou, China
| | - Zheng Chen
- Department of Pediatrics, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.
| | - Raul E Guzman
- Institute of Biological Information Processing (IBI-1), Molecular and Cell Physiology, Jülich Research Center, Jülich, Germany.
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Sahly AN, Sierra-Marquez J, Bungert-Plümke S, Franzen A, Mougharbel L, Berrahmoune S, Dassi C, Poulin C, Srour M, Guzman RE, Myers KA. Genotype-phenotype correlation in CLCN4-related developmental and epileptic encephalopathy. Hum Genet 2024; 143:667-681. [PMID: 38578438 DOI: 10.1007/s00439-024-02668-z] [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: 02/17/2024] [Accepted: 03/07/2024] [Indexed: 04/06/2024]
Abstract
CLCN4-related disorder is a rare X-linked neurodevelopmental condition with a pathogenic mechanism yet to be elucidated. CLCN4 encodes the vesicular 2Cl-/H+ exchanger ClC-4, and CLCN4 pathogenic variants frequently result in altered ClC-4 transport activity. The precise cellular and molecular function of ClC-4 remains unknown; however, together with ClC-3, ClC-4 is thought to have a role in the ion homeostasis of endosomes and intracellular trafficking. We reviewed our research database for patients with CLCN4 variants and epilepsy, and performed thorough phenotyping. We examined the functional properties of the variants in mammalian cells using patch-clamp electrophysiology, protein biochemistry, and confocal fluorescence microscopy. Three male patients with developmental and epileptic encephalopathy were identified, with differing phenotypes. Patients #1 and #2 had normal growth parameters and normal-appearing brains on MRI, while patient #3 had microcephaly, microsomia, complete agenesis of the corpus callosum and cerebellar and brainstem hypoplasia. The p.(Gly342Arg) variant of patient #1 significantly impaired ClC-4's heterodimerization capability with ClC-3 and suppressed anion currents. The p.(Ile549Leu) variant of patient #2 and p.(Asp89Asn) variant of patient #3 both shift the voltage dependency of transport activation by 20 mV to more hyperpolarizing potentials, relative to the wild-type, with p.(Asp89Asn) favouring higher transport activity. We concluded that p.(Gly342Arg) carried by patient #1 and the p.(Ile549Leu) expressed by patient #2 impair ClC-4 transport function, while the p.(Asp89Asn) variant results in a gain-of-transport function; all three variants result in epilepsy and global developmental impairment, but with differences in epilepsy presentation, growth parameters, and presence or absence of brain malformations.
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Affiliation(s)
- Ahmed N Sahly
- Division of Neurology, Department of Pediatrics, Montreal Children's Hospital, McGill University Health Centre, Montreal, QC, Canada
- Department of Neurosciences, King Faisal Specialist Hospital & Research Centre, Jeddah, Saudi Arabia
| | - Juan Sierra-Marquez
- Institute of Biological Information Processing; Biological Molecular and Cell Physiology (IBI-1), Molecular and Cell Physiology, Research Center Jülich , GmbH Leo-Brandt-Strasse 1, 52428, Jülich, Germany
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Stefanie Bungert-Plümke
- Institute of Biological Information Processing; Biological Molecular and Cell Physiology (IBI-1), Molecular and Cell Physiology, Research Center Jülich , GmbH Leo-Brandt-Strasse 1, 52428, Jülich, Germany
| | - Arne Franzen
- Institute of Biological Information Processing; Biological Molecular and Cell Physiology (IBI-1), Molecular and Cell Physiology, Research Center Jülich , GmbH Leo-Brandt-Strasse 1, 52428, Jülich, Germany
| | - Lina Mougharbel
- Research Institute of the McGill University Medical Centre, Montreal, QC, Canada
| | - Saoussen Berrahmoune
- Research Institute of the McGill University Medical Centre, Montreal, QC, Canada
| | - Christelle Dassi
- Research Institute of the McGill University Medical Centre, Montreal, QC, Canada
| | - Chantal Poulin
- Division of Neurology, Department of Pediatrics, Montreal Children's Hospital, McGill University Health Centre, Montreal, QC, Canada
- Department of Neurology and Neurosurgery, Montreal Children's Hospital, McGill University Health Centre, 1001 Boulevard Décarie, Montreal, PQ, H4A 3J1, Canada
| | - Myriam Srour
- Division of Neurology, Department of Pediatrics, Montreal Children's Hospital, McGill University Health Centre, Montreal, QC, Canada
- Research Institute of the McGill University Medical Centre, Montreal, QC, Canada
- Department of Neurology and Neurosurgery, Montreal Children's Hospital, McGill University Health Centre, 1001 Boulevard Décarie, Montreal, PQ, H4A 3J1, Canada
| | - Raul E Guzman
- Institute of Biological Information Processing; Biological Molecular and Cell Physiology (IBI-1), Molecular and Cell Physiology, Research Center Jülich , GmbH Leo-Brandt-Strasse 1, 52428, Jülich, Germany.
| | - Kenneth A Myers
- Division of Neurology, Department of Pediatrics, Montreal Children's Hospital, McGill University Health Centre, Montreal, QC, Canada.
- Research Institute of the McGill University Medical Centre, Montreal, QC, Canada.
- Department of Neurology and Neurosurgery, Montreal Children's Hospital, McGill University Health Centre, 1001 Boulevard Décarie, Montreal, PQ, H4A 3J1, Canada.
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Picollo A. Vesicular CLC chloride/proton exchangers in health and diseases. Front Pharmacol 2023; 14:1295068. [PMID: 38027030 PMCID: PMC10662042 DOI: 10.3389/fphar.2023.1295068] [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: 09/15/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
Chloride is one of the most abundant anions in the human body; it is implicated in several physiological processes such as the transmission of action potentials, transepithelial salt transport, maintenance of cellular homeostasis, regulation of osmotic pressure and intracellular pH, and synaptic transmission. The balance between the extracellular and intracellular chloride concentrations is controlled by the interplay of ion channels and transporters embedded in the cellular membranes. Vesicular members of the CLC chloride protein family (vCLCs) are chloride/proton exchangers expressed in the membrane of the intracellular organelles, where they control vesicular acidification and luminal chloride concentration. It is well known that mutations in CLCs cause bone, kidney, and lysosomal genetic diseases. However, the role of CLC exchangers in neurological disorders is only now emerging with the identification of pathogenic CLCN gene variants in patients with severe neuronal and intellectual dysfunctions. This review will provide an overview of the recent advances in understanding the role of the vesicular CLC chloride/proton exchangers in human pathophysiology.
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Affiliation(s)
- Alessandra Picollo
- Institute of Biophysics, National Research Council, Genova, Italy
- RAISE Ecosystem, Genova, Italy
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Li S, Zhang W, Liang P, Zhu M, Zheng B, Zhou W, Wang C, Zhao X. Novel variants in the CLCN4 gene associated with syndromic X-linked intellectual disability. Front Neurol 2023; 14:1096969. [PMID: 37789889 PMCID: PMC10542403 DOI: 10.3389/fneur.2023.1096969] [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: 11/13/2022] [Accepted: 08/15/2023] [Indexed: 10/05/2023] Open
Abstract
Objective The dysfunction of the CLCN4 gene can lead to X-linked intellectual disability and Raynaud-Claes syndrome (MRXSRC), characterized by severe cognitive impairment and mental disorders. This study aimed to investigate the genetic defects and clinical features of Chinese children with CLCN4 variants and explore the effect of mutant ClC-4 on the protein expression level and subcellular localization through in vitro experiments. Methods A total of 401 children with intellectual disabilities were screened for genetic variability using whole-exome sequencing (WES). Clinical data, including age, sex, perinatal conditions, and environmental exposure, were collected. Cognitive, verbal, motor, and social behavioral abilities were evaluated. Candidate variants were verified using Sanger sequencing, and their pathogenicity and conservation were analyzed using in silico prediction tools. Protein expression and localization of mutant ClC-4 were measured using Western blotting (WB) and immunofluorescence microscopy. The impact of a splice site variant was assessed with a minigene assay. Results Exome analysis identified five rare CLCN4 variants in six unrelated patients with intellectual disabilities, including two recurrent heterozygous de novo missense variants (p.D89N and p.A555V) in three female patients, and two hemizygous missense variants (p.N141S and p.R694Q) and a splicing variant (c.1390-12T > G) that are maternally inherited in three male patients. The p.N141S variant and the splicing variant c.1390-12(T > G were novel, while p.R694Q was identified in two asymptomatic heterozygous female patients. The six children with CLCN4 variants exhibited a neurodevelopmental spectrum disease characterized by intellectual disability (ID), delayed speech, autism spectrum disorders (ASD), microcephaly, hypertonia, and abnormal imaging findings. The minigene splicing result indicated that the c.1390-12T > G did not affect the splicing of CLCN4 mRNA. In vitro experiments showed that the mutant protein level and localization of mutant protein are similar to the wild type. Conclusion The study identified six probands with CLCN4 gene variants associated with X-linked ID. It expanded the gene and phenotype spectrum of CLCN4 variants. The bioinformatic analysis supported the pathogenicity of CLCN4 variants. However, these CLCN4 gene variants did not affect the ClC-4 expression levels and protein location, consistent with previous studies. Further investigations are necessary to investigate the pathogenetic mechanism.
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Affiliation(s)
- Sinan Li
- Department of Rehabilitation, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Wenxin Zhang
- Department of Rehabilitation, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Piao Liang
- Department of Rehabilitation, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Min Zhu
- Department of Rehabilitation, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Bixia Zheng
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Wei Zhou
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Chunli Wang
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Xiaoke Zhao
- Department of Rehabilitation, Children's Hospital of Nanjing Medical University, Nanjing, China
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Rossi J, Russo M, Gobbi G, Terracciano A, Zuntini R, Giuseppe Caraffi S, Novelli A, Garavelli L, Valzania F, Rizzi R. Developmental and epileptic encephalopathy in a young Italian woman with a de novo missense variant in the CLCN4 gene: A case report. Brain Dev 2023; 45:445-450. [PMID: 37271660 DOI: 10.1016/j.braindev.2023.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/27/2023] [Accepted: 05/15/2023] [Indexed: 06/06/2023]
Abstract
INTRODUCTION Raynaud-Claes syndrome is a very rare X-linked condition, characterized by intellectual disability, impaired language development, brain abnormalities, facial dysmorphisms and drug-resistant epilepsy. It is caused by loss-of-function variants in the CLCN4 gene, which encodes the 2Cl-/H + exchanger ClC-4, prominently expressed in the hippocampus and cerebellum. Different genotypic variants have been described, each exhibiting specific phenotypic characteristics. The loss-of-function variant p.Gly544Arg in the CLCN4 gene has been described in only two male probands, but there are no reports on phenotypic characterization in females. CASE PRESENTATION We present a 30-year-old Italian woman with early-onset drug-resistant epilepsy, developmental and epileptic encephalopathy, developmental delay, absence of verbal language development, behavioral impairment with autistic features, and clusters of seizures during catamenial periods. The interictal EEG showed slight inconstant slowing of the background rhythm, with abnormal frontal predominant mu like rhythm and generalized spike and polyspike wave discharges, which increased in frequency during drowsiness. A brain MRI showed slight cranio-encephalic asymmetry and a smaller size of the left hippocampus. The whole exome sequencing (WES) revealed a de novo heterozygous c.1630G > A variant in the CLCN4 gene, resulting in the amino acid substitution p.Gly544Arg (rs587777161), consistent with Raynaud-Claes syndrome. DISCUSSION AND CONCLUSION Our patient is the first case of a de novo p.Gly544Arg variant of the CLCN4 gene in a female proband, confirming that female patients with Raynaud-Claes syndrome can be as severely affected as the male counterparts. Our case expands the phenotypic characterization of different genotypic CLCN4 variants, which can become crucial in the future for early diagnosis if targeted therapy becomes available.
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Affiliation(s)
- Jessica Rossi
- Clinical and Experimental Medicine PhD Program, University of Modena and Reggio Emilia, Modena, Italy; Neuromotor & Rehabilitation Department, Neurology Unit, Azienda USL-IRCCS of Reggio Emilia, Reggio Emilia, Italy
| | - Marco Russo
- Neuromotor & Rehabilitation Department, Neurology Unit, Azienda USL-IRCCS of Reggio Emilia, Reggio Emilia, Italy
| | - Giuseppe Gobbi
- Chairman of the Scientific Commettee ASSOCIAZIONE ITALIANA EPILESSIA (AIE), Italia Odv, Italy
| | - Alessandra Terracciano
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy
| | - Roberta Zuntini
- Medical Genetics Unit, Azienda USL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy
| | | | - Antonio Novelli
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy
| | - Livia Garavelli
- Medical Genetics Unit, Azienda USL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy
| | - Franco Valzania
- Neuromotor & Rehabilitation Department, Neurology Unit, Azienda USL-IRCCS of Reggio Emilia, Reggio Emilia, Italy
| | - Romana Rizzi
- Neuromotor & Rehabilitation Department, Neurology Unit, Azienda USL-IRCCS of Reggio Emilia, Reggio Emilia, Italy.
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Functional and clinical studies reveal pathophysiological complexity of CLCN4-related neurodevelopmental condition. Mol Psychiatry 2023; 28:668-697. [PMID: 36385166 PMCID: PMC9908558 DOI: 10.1038/s41380-022-01852-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 10/10/2022] [Accepted: 10/21/2022] [Indexed: 11/17/2022]
Abstract
Missense and truncating variants in the X-chromosome-linked CLCN4 gene, resulting in reduced or complete loss-of-function (LOF) of the encoded chloride/proton exchanger ClC-4, were recently demonstrated to cause a neurocognitive phenotype in both males and females. Through international clinical matchmaking and interrogation of public variant databases we assembled a database of 90 rare CLCN4 missense variants in 90 families: 41 unique and 18 recurrent variants in 49 families. For 43 families, including 22 males and 33 females, we collated detailed clinical and segregation data. To confirm causality of variants and to obtain insight into disease mechanisms, we investigated the effect on electrophysiological properties of 59 of the variants in Xenopus oocytes using extended voltage and pH ranges. Detailed analyses revealed new pathophysiological mechanisms: 25% (15/59) of variants demonstrated LOF, characterized by a "shift" of the voltage-dependent activation to more positive voltages, and nine variants resulted in a toxic gain-of-function, associated with a disrupted gate allowing inward transport at negative voltages. Functional results were not always in line with in silico pathogenicity scores, highlighting the complexity of pathogenicity assessment for accurate genetic counselling. The complex neurocognitive and psychiatric manifestations of this condition, and hitherto under-recognized impacts on growth, gastrointestinal function, and motor control are discussed. Including published cases, we summarize features in 122 individuals from 67 families with CLCN4-related neurodevelopmental condition and suggest future research directions with the aim of improving the integrated care for individuals with this diagnosis.
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Guzman RE, Sierra-Marquez J, Bungert-Plümke S, Franzen A, Fahlke C. Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy. Front Mol Neurosci 2022; 15:872407. [PMID: 35721313 PMCID: PMC9198718 DOI: 10.3389/fnmol.2022.872407] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 04/27/2022] [Indexed: 11/13/2022] Open
Abstract
Early/late endosomes, recycling endosomes, and lysosomes together form the endo-lysosomal recycling pathway. This system plays a crucial role in cell differentiation and survival, and dysregulation of the endo-lysosomal system appears to be important in the pathogenesis of neurodevelopmental and neurodegenerative diseases. Each endo-lysosomal compartment fulfils a specific function, which is supported by ion transporters and channels that modify ion concentrations and electrical gradients across endo-lysosomal membranes. CLC-type Cl–/H+ exchangers are a group of endo-lysosomal transporters that are assumed to regulate luminal acidification and chloride concentration in multiple endosomal compartments. Heterodimers of ClC-3 and ClC-4 localize to various internal membranes, from the endoplasmic reticulum and Golgi to recycling endosomes and late endosomes/lysosomes. The importance of ClC-4-mediated ion transport is illustrated by the association of naturally occurring CLCN4 mutations with epileptic encephalopathy, intellectual disability, and behavioral disorders in human patients. However, how these mutations affect the expression, subcellular localization, and function of ClC-4 is insufficiently understood. We here studied 12 CLCN4 variants that were identified in patients with X-linked intellectual disability and epilepsy and were already characterized to some extent in earlier work. We analyzed the consequences of these mutations on ClC-4 ion transport, subcellular trafficking, and heterodimerization with ClC-3 using heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings. The mutations led to a variety of changes in ClC-4 function, ranging from gain/loss of function and impaired heterodimerization with ClC-3 to subtle impairments in transport functions. Our results suggest that even slight functional changes to the endosomal Cl–/H+ exchangers can cause serious neurological symptoms.
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