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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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Kavanaugh BC, Elacio J, Best CR, St Pierre DG, Pescosolido MF, Ouyang Q, Caruso P, Buch K, Biedermann J, Bradley RS, Liu JS, Jones RN, Morrow EM. Christianson Syndrome across the Lifespan: An International Longitudinal Study in Children, Adolescents, and Adults. medRxiv 2023:2023.11.11.23298218. [PMID: 37987014 PMCID: PMC10659496 DOI: 10.1101/2023.11.11.23298218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Mutations in the X-linked endosomal Na+/H+ Exchanger 6 (NHE6) causes Christianson Syndrome (CS). In the largest study to date, we examine genetic diversity and clinical progression, including cerebellar degeneration, in CS into adulthood. Data were collected as part of the International Christianson Syndrome and NHE6 (SLC9A6) Gene Network Study. Forty-four individuals with 31 unique NHE6 mutations, age 2 to 32 years, were followed prospectively, herein reporting baseline, 1-year follow-up, and retrospective natural history. We present data on the CS phenotype with regard to physical growth, adaptive and motor regression, and 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 (18+ years) participants lost gross and fine motor skills over a 1-year follow-up. Previously defined core diagnostic criteria for CS (present in >85%) - namely nonverbal status, intellectual disability, epilepsy, postnatal microcephaly, ataxia, hyperkinesia - were universally present in age 6 to 16; however, an additional core feature of high pain tolerance was added (present in 91%), and furthermore, evolution of symptoms were noted across the lifespan, such that postnatal microcephaly, ataxia and high pain threshold were often not apparent prior to age 6, and hyperkinesis decreased after age 16. While neurologic exams 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. 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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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. bioRxiv 2023:2023.11.08.565997. [PMID: 37986849 PMCID: PMC10659387 DOI: 10.1101/2023.11.08.565997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Mutations in the endosomal Na+/H+ exchanger (NHE6) cause Christianson syndrome (CS), an X-linked neurological disorder. Previous studies have shown that 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, ARF binding protein 1 (GGA1) as an interacting partner for NHE6. We corroborated the NHE6-GGA1 interaction using co-immunoprecipitation (co-IP): using over-expressed constructs in mammalian cells; and co-IP of endogenously-expressed GGA1 and NHE6 from neuroblastoma cells, as well as from mouse brain. We demonstrate that GGA1 interacts with organellar NHEs (NHE6, NHE7 and NHE9) but not with cell-surface localized NHEs (NHE1 and NHE5). By constructing hybrid NHE1/NHE6 exchangers, we demonstrate that the cytoplasmic tail of NHE6 is necessary and sufficient for interactions with GGA1. We demonstrate the co-localization 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 mis-localized in GGA1 knockout 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 mis-localization, and Golgi retention, we find the intra-luminal pH in Golgi to be alkalinized. Our study demonstrates a new interaction between NHE6 and GGA1 which functions in the localization of this intra-cellular NHE to the endosome compartment.
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Pruett BS, Pinner AL, Kim P, Meador-Woodruff JH. Altered distribution and localization of organellar Na(+)/H(+) exchangers in postmortem schizophrenia dorsolateral prefrontal cortex. Transl Psychiatry 2023; 13:34. [PMID: 36732328 DOI: 10.1038/s41398-023-02336-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [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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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Gómez-Mellado VE, Ho-Mok KS, van der Mark VA, van der Wel NN, Grootemaat AE, Verhoeven AJ, Elferink RPJO, Paulusma CC. The phospholipid flippase ATP8B1 is required for lysosomal fusion in macrophages. Cell Biochem Funct 2022; 40:914-925. [PMID: 36169099 PMCID: PMC10087937 DOI: 10.1002/cbf.3752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 09/08/2022] [Accepted: 09/12/2022] [Indexed: 12/15/2022]
Abstract
ATP8B1 is a phospholipid flippase and member of the type 4 subfamily of P-type ATPases (P4-ATPase) subfamily. P4-ATPases catalyze the translocation of phospholipids across biological membranes, ensuring proper membrane asymmetry, which is crucial for membrane protein targeting and activity, vesicle biogenesis, and barrier function. Here we have investigated the role of ATP8B1 in the endolysosomal pathway in macrophages. Depletion of ATP8B1 led to delayed degradation of content in the phagocytic pathway and in overacidification of the endolysosomal system. Furthermore, ATP8B1 knockdown cells exhibited large multivesicular bodies filled with intraluminal vesicles. Similar phenotypes were observed in CRISPR-generated ATP8B1 knockout cells. Importantly, induction of autophagy led to accumulation of autophagosomes in ATP8B1 knockdown cells. Collectively, our results support a novel role for ATP8B1 in lysosomal fusion in macrophages, a process crucial in the terminal phase of endolysosomal degradation.
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Affiliation(s)
- Valentina E Gómez-Mellado
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Kam S Ho-Mok
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Vincent A van der Mark
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Nicole N van der Wel
- Department of Medical Biology, Electron Microscopy Center Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Anita E Grootemaat
- Department of Medical Biology, Electron Microscopy Center Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Arthur J Verhoeven
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Ronald P J Oude Elferink
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Coen C Paulusma
- Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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11
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [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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13
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Iraninasab S, Sharifian S, Homaei A, Homaee MB, Sharma T, Nadda AK, Kennedy JF, Bilal M, Iqbal HMN. Emerging trends in environmental and industrial applications of marine carbonic anhydrase: a review. Bioprocess Biosyst Eng 2022; 45:431-451. [PMID: 34821989 DOI: 10.1007/s00449-021-02667-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/10/2021] [Indexed: 02/08/2023]
Abstract
Biocatalytic conversion of greenhouse gases such as carbon dioxide into commercial products is one of the promising key approaches to solve the problem of climate change. Microbial enzymes, including carbonic anhydrase, NAD-dependent formate dehydrogenase, ribulose bisphosphate carboxylase, and methane monooxygenase, have been exploited to convert atmospheric gases into industrial products. Carbonic anhydrases are Zn2+-dependent metalloenzymes that catalyze the reversible conversion of CO2 into bicarbonate. They are widespread in bacteria, algae, plants, and higher organisms. In higher organisms, they regulate the physiological pH and contribute to CO2 transport in the blood. In plants, algae, and photosynthetic bacteria carbonic anhydrases are involved in photosynthesis. Converting CO2 into bicarbonate by carbonic anhydrases can solidify gaseous CO2, thereby reducing global warming due to the burning of fossil fuels. This review discusses the three-dimensional structures of carbonic anhydrases, their physiological role in marine life, their catalytic mechanism, the types of inhibitors, and their medicine and industry applications.
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Affiliation(s)
- Sudabeh Iraninasab
- Department of Marine Biology, Faculty of Marine Science and Technology, University of Hormozgan, P.O. Box 3995, Bandar Abbas, Iran
| | - Sana Sharifian
- Department of Marine Biology, Faculty of Marine Science and Technology, University of Hormozgan, P.O. Box 3995, Bandar Abbas, Iran
| | - Ahmad Homaei
- Department of Marine Biology, Faculty of Marine Science and Technology, University of Hormozgan, P.O. Box 3995, Bandar Abbas, Iran.
| | | | - Tanvi Sharma
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173 234, India
| | - Ashok Kumar Nadda
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, 173 234, India
| | - John F Kennedy
- Chembiotech Laboratories, Advanced Science and Technology Institute, The Kyrewood Centre, Tenbury Wells, Worcs, WR15 8FF, UK
| | - Muhammad Bilal
- School of Life Science and Food Engineering, Huaiyin Institute of Technology, Huaian, 223003, China
| | - Hafiz M N Iqbal
- Tecnologico de Monterrey, School of Engineering and Sciences, 64849, Monterrey, Mexico
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14
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Schnyder D, Albano G, Kucharczyk P, Dolder S, Siegrist M, Anderegg M, Pathare G, Hofstetter W, Baron R, Fuster DG. Deletion of the sodium/hydrogen exchanger 6 causes low bone volume in adult mice. Bone 2021; 153:116178. [PMID: 34508879 DOI: 10.1016/j.bone.2021.116178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 09/04/2021] [Accepted: 09/05/2021] [Indexed: 11/18/2022]
Abstract
The sodium/hydrogen exchanger 6 (NHE6) localizes to recycling endosomes, where it mediates endosomal alkalinization through K+/H+ exchange. Mutations in the SLC9A6 gene encoding NHE6 cause severe X-linked mental retardation, epilepsy, autism and corticobasal degeneration in humans. Patients with SLC9A6 mutations exhibit skeletal malformations, and a previous study suggested a key role of NHE6 in osteoblast-mediated mineralization. The goal of this study was to explore the role of NHE6 in bone homeostasis. To this end, we studied the bone phenotype of NHE6 knock-out mice by microcomputed tomography, quantitative histomorphometry and complementary ex vivo and in vitro studies. We detected NHE6 transcript and protein in both differentiated osteoclasts and mineralizing osteoblasts. In vitro studies with osteoclasts and osteoblasts derived from NHE6 knock-out mice demonstrated normal osteoclast differentiation and osteoblast proliferation without an impairment in mineralization capacity. Microcomputed tomography and bone histomorphometry studies showed a significantly reduced bone volume and trabecular number as well as an increased trabecular space at lumbar vertebrae of 6 months old NHE6 knock-out mice. The bone degradation marker c-terminal telopeptides of type I collagen was unaltered in NHE6 knock-out mice. However, we observed a reduction of the bone formation marker procollagen type 1 N-terminal propeptide, and increased circulating sclerostin levels in NHE6 knock-out mice. Subsequent studies revealed a significant upregulation of sclerostin transcript expression in both primary calvarial cultures and femora derived from NHE6 knock-out mice. Thus, loss of NHE6 in mice causes an increase of sclerostin expression associated with reduced bone formation and low bone volume.
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Affiliation(s)
- Daniela Schnyder
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Giuseppe Albano
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Patrycja Kucharczyk
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Silvia Dolder
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Mark Siegrist
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Manuel Anderegg
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Ganesh Pathare
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Willy Hofstetter
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Roland Baron
- Division of Bone and Mineral Research, Harvard Medical School and Harvard School of Dental Medicine, Boston, MA, USA; Department of Oral Medicine, Infection and Immunity, Harvard Medical School and Harvard School of Dental Medicine, Boston, MA, USA
| | - Daniel G Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland.
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15
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Mir A, Almudhry M, Alghamdi F, Albaradie R, Ibrahim M, Aldurayhim F, Alhedaithy A, Alamr M, Bawazir M, Mohammad S, Abdelhay S, Bashir S, Housawi Y. SLC gene mutations and pediatric neurological disorders: diverse clinical phenotypes in a Saudi Arabian population. Hum Genet 2021; 141:81-99. [PMID: 34797406 DOI: 10.1007/s00439-021-02404-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 11/12/2021] [Indexed: 12/12/2022]
Abstract
The uptake and efflux of solutes across a plasma membrane is controlled by transporters. There are two main superfamilies of transporters, adenosine 5'-triphosphate (ATP) binding cassettes (ABCs) and solute carriers (SLCs). In the brain, SLC transporters are involved in transporting various solutes across the blood-brain barrier, blood-cerebrospinal fluid barrier, astrocytes, neurons, and other brain cell types including oligodendrocytes and microglial cells. SLCs play an important role in maintaining normal brain function. Hence, mutations in the genes that encode SLC transporters can cause a variety of neurological disorders. We identified the following SLC gene variants in 25 patients in our cohort: SLC1A2, SLC2A1, SLC5A1, SLC6A3, SLC6A5, SLC6A8, SLC9A6, SLC9A9, SLC12A6, SLC13A5, SLC16A1, SLC17A5, SLC19A3, SLC25A12, SLC25A15, SLC27A4, SLC45A1, SLC46A1, and SLC52A3. Eight patients harbored pathogenic or likely pathogenic mutations (SLC5A1, SLC9A6, SLC12A6, SLC16A1, SLC19A3, and SLC52A3), and 12 patients were found to have variants of unknown clinical significance (VOUS); these variants occurred in 11 genes (SLC1A2, SLC2A1, SLC6A3, SLC6A5, SLC6A8, SLC9A6, SLC9A9, SLC13A5, SLC25A12, SLC27A4, and SLC45A1). Five patients were excluded as they were carriers. In the remaining 20 patients with SLC gene variants, we identified 16 possible distinct neurological disorders. Based on the clinical presentation, we categorized them into genes causing intellectual delay (ID) or autism spectrum disorder (ASD), those causing epilepsy, those causing vitamin-related disorders, and those causing other neurological diseases. Several variants were detected that indicated possible personalized therapies: SLC2A1 led to dystonia or epilepsy, which can be treated with a ketogenic diet; SLC6A3 led to infantile parkinsonism-dystonia 1, which can be treated with levodopa; SLC6A5 led to hyperekplexia 3, for which unnecessary treatment with antiepileptic drugs should be avoided; SLC6A8 led to creatine deficiency syndrome type 1, which can be treated with creatine monohydrate; SLC16A1 led to monocarboxylate transporter 1 deficiency, which causes seizures that should not be treated with a ketogenic diet; SLC19A3 led to biotin-thiamine-responsive basal ganglia disease, which can be treated with biotin and thiamine; and SLC52A3 led to Brown-Vialetto-Van-Laere syndrome 1, which can be treated with riboflavin. The present study examines the prevalence of SLC gene mutations in our cohort of children with epilepsy and other neurological disorders. It highlights the diverse phenotypes associated with mutations in this large family of SLC transporter proteins, and an opportunity for personalized genomics and personalized therapeutics.
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Affiliation(s)
- Ali Mir
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia.
| | - Montaha Almudhry
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Fouad Alghamdi
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Raidah Albaradie
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Mona Ibrahim
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Fatimah Aldurayhim
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Abdullah Alhedaithy
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Mushari Alamr
- Genetic and Metabolic Department, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia
| | - Maryam Bawazir
- Genetic and Metabolic Department, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia
| | - Sahar Mohammad
- Department of Pediatric, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia
| | - Salma Abdelhay
- Department of Pediatric, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia
| | - Shahid Bashir
- Department of Pediatric Neurology, Neuroscience Center, King Fahad Specialist Hospital, Ammar Bin Thabit Street, Dammam, 31444, Kingdom of Saudi Arabia
| | - Yousef Housawi
- Genetic and Metabolic Department, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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17
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Park HJ, Choi I, Leem KH. Decreased Brain pH and Pathophysiology in Schizophrenia. Int J Mol Sci 2021; 22:8358. [PMID: 34445065 DOI: 10.3390/ijms22168358] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 07/30/2021] [Accepted: 07/30/2021] [Indexed: 12/26/2022] Open
Abstract
Postmortem studies reveal that the brain pH in schizophrenia patients is lower than normal. The exact cause of this low pH is unclear, but increased lactate levels due to abnormal energy metabolism appear to be involved. Schizophrenia patients display distinct changes in mitochondria number, morphology, and function, and such changes promote anaerobic glycolysis, elevating lactate levels. pH can affect neuronal activity as H+ binds to numerous proteins in the nervous system and alters the structure and function of the bound proteins. There is growing evidence of pH change associated with cognition, emotion, and psychotic behaviors. Brain has delicate pH regulatory mechanisms to maintain normal pH in neurons/glia and extracellular fluid, and a change in these mechanisms can affect, or be affected by, neuronal activities associated with schizophrenia. In this review, we discuss the current understanding of the cause and effect of decreased brain pH in schizophrenia based on postmortem human brains, animal models, and cellular studies. The topic includes the factors causing decreased brain pH in schizophrenia, mitochondria dysfunction leading to altered energy metabolism, and pH effects on the pathophysiology of schizophrenia. We also review the acid/base transporters regulating pH in the nervous system and discuss the potential contribution of the major transporters, sodium hydrogen exchangers (NHEs), and sodium-coupled bicarbonate transporters (NCBTs), to schizophrenia.
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18
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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19
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Gong P, Xue J, Jiao X, Zhang Y, Yang Z. Genetic Etiologies in Developmental and/or Epileptic Encephalopathy With Electrical Status Epilepticus During Sleep: Cohort Study. Front Genet 2021; 12:607965. [PMID: 33897753 PMCID: PMC8060571 DOI: 10.3389/fgene.2021.607965] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 03/02/2021] [Indexed: 11/30/2022] Open
Abstract
Background Recently, the electroencephalogram pattern of electrical status epilepticus during sleep (ESES) had been reported in some genetic disorders, and most of them were noted with developmental and epileptic encephalopathy (DEE) or epileptic encephalopathy (EE). This study aimed to determine the genetic etiologies and clinical characteristics of ESES in DEE/EE. Methods We performed a cohort study in cases of DEE or EE with ESES. Tio-based genetic testing was performed in 74 cases and was analyzed to identify underlying variants. Results Pathogenic or likely pathogenic variants were identified in 17/74 cases, including KCNQ2 (n = 6), KCNA2 (n = 5), GRIN2A (n = 3), SLC9A6 (n = 1), HIVEP2 (n = 1), and RARS2 (n = 1). Eleven were boys. The median age at seizure onset was 6 months. ESES occurred at the mean age of 2.0 ± 1.2 years, predominant in the Rolandic region in 14 years. Twelve of 17 cases had the first stage of different epilepsy preceding ESES: 2/12 were diagnosed as Ohtahara syndrome, 2/12 were diagnosed as infantile spasms, 3/12 were diagnosed as DEE, and 5/12 were diagnosed as EE without the epileptic syndrome. Conclusion Monogenic variants explained over 20% of DEE/EE with ESES. ESES could be an age-related feature in genetic disorders and occurred after the first stage of different epilepsy. Both age-related factors and genetic etiology were suggested to play a role in the occurrence of ESES in genetic DEE/EE.
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Affiliation(s)
- Pan Gong
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Jiao Xue
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xianru Jiao
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Yuehua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
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20
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Petitjean H, Fatima T, Mouchbahani-Constance S, Davidova A, Ferland CE, Orlowski J, Sharif-Naeini R. Loss of SLC9A6/NHE6 impairs nociception in a mouse model of Christianson syndrome. Pain 2020; 161:2619-28. [PMID: 32569089 DOI: 10.1097/j.pain.0000000000001961] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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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21
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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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22
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Sun S, Chen L, Wang Y, Wang J, Li N, Wang X. Further delineation of autosomal recessive intellectual disability syndrome caused by homozygous variant of the NSUN2 gene in a chinese pedigree. Mol Genet Genomic Med 2020; 8:e1518. [PMID: 33002343 PMCID: PMC7767538 DOI: 10.1002/mgg3.1518] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/03/2020] [Accepted: 09/17/2020] [Indexed: 11/06/2022] Open
Abstract
Background The enzyme NOP2/Sun RNA methyltransferase 2 (NSUN2) catalyzes the methylation of cytosine to 5‐methylcytosine (m5C) at position 34 of tRNA(Leu; CAA) precursors containing introns that play a vital role in spindle assembly during mitosis and chromosome segregation. Biallelic variants in the NSUN2 gene cause a rare intellectual disability that has been identified only in a few Middle Eastern patients. Affected individuals usually have other deformities, including developmental delay, short stature, microcephaly, and facial dysmorphism. The aim of this study was to identify the genetic cause of three female patients from a Chinese pedigree, who presented with similar phenotype consisting of the above clinical features. Methods Whole‐exome sequencing (WES) was used to screen for causal variants in the genome, and the candidate variants were subsequently verified using Sanger sequencing. Results WES revealed a previously unreported homozygous nonsense variant (NM_017755.5: c.1004T>A, p.Leu335*) in exon 9 of NSUN2, which was consistent with the clinical phenotype of the patients and co‐segregated with the disease in their family. A comparison of this phenotype with that of patients in published reports uncovered several novel clinical features related to NSUN2 variations, including feeding difficulties, slender hands and fingers, severely restricted finger mobility, hallux valgus, varus foot, and elevated α‐hydroxybutyrate dehydrogenase (HBDH). Conclusions These are the first findings of a non‐consanguineous Chinese pedigree with a homozygous NSUN2 variant. We expanded the phenotypic spectrum associated with NSUN2 variations.
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Affiliation(s)
| | - Lin Chen
- Department of Pediatric, Guizhou Provincial People's Hospital, Guizhou University, Guiyang, China
| | - Yuchuan Wang
- Department of Pediatric, Guizhou Provincial People's Hospital, Guizhou University, Guiyang, China
| | - Jian Wang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Niu Li
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Xike Wang
- Department of Pediatric, Guizhou Provincial People's Hospital, Guizhou University, Guiyang, China
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23
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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24
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Kucharava K, Brand Y, Albano G, Sekulic-Jablanovic M, Glutz A, Xian X, Herz J, Bodmer D, Fuster DG, Petkovic V. Sodium-hydrogen exchanger 6 (NHE6) deficiency leads to hearing loss, via reduced endosomal signalling through the BDNF/Trk pathway. Sci Rep 2020; 10:3609. [PMID: 32107410 PMCID: PMC7046661 DOI: 10.1038/s41598-020-60262-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 02/07/2020] [Indexed: 01/03/2023] Open
Abstract
Acid-base homeostasis is critical for normal growth, development, and hearing function. The sodium-hydrogen exchanger 6 (NHE6), a protein mainly expressed in early and recycling endosomes, plays an important role in regulating organellar pH. Mutations in NHE6 cause complex, slowly progressive neurodegeneration. Little is known about NHE6 function in the mouse cochlea. Here, we found that all NHE isoforms were expressed in wild-type (WT) mouse cochlea. Nhe6 knockout (KO) mice showed significant hearing loss compared to WT littermates. Immunohistochemistry in WT mouse cochlea showed that Nhe6 was localized in the organ of Corti (OC), spiral ganglion (SG), stria vascularis (SV), and afferent nerve fibres. The middle and the inner ears of WT and Nhe6 KO mice were not different morphologically. Given the putative role of NHE6 in early endosomal function, we examined Rab GTPase expression in early and late endosomes. We found no change in Rab5, significantly lower Rab7, and higher Rab11 levels in the Nhe6 KO OC, compared to WT littermates. Because Rabs mediate TrkB endosomal signalling, we evaluated TrkB phosphorylation in the OCs of both strains. Nhe6 KO mice showed significant reductions in TrkB and Akt phosphorylation in the OC. In addition, we examined genes used as markers of SG type I (Slc17a7, Calb1, Pou4f1, Cal2) and type II neurons (Prph, Plk5, Cacna1g). We found that all marker gene expression levels were significantly elevated in the SG of Nhe6 KO mice, compared to WT littermates. Anti-neurofilament factor staining showed axon loss in the cochlear nerves of Nhe6 KO mice compared to WT mice. These findings indicated that BDNF/TrkB signalling was disrupted in the OC of Nhe6 KO mice, probably due to TrkB reduction, caused by over acidification in the absence of NHE6. Thus, our findings demonstrated that NHEs play important roles in normal hearing in the mammalian cochlea.
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Affiliation(s)
- Krystsina Kucharava
- Department of Biomedicine, and Clinic for Otolaryngology, Head and Neck Surgery, Hospital Basel, University of Basel, Basel, 4031, Switzerland
| | - Yves Brand
- Clinic for Otolaryngology, Head and Neck Surgery, Kantonsspital Graubünden, Chur, 7000, Switzerland
| | - Giuseppe Albano
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, and NCCR Transcure, University of Bern, Bern, Switzerland
| | - Marijana Sekulic-Jablanovic
- Department of Biomedicine, and Clinic for Otolaryngology, Head and Neck Surgery, Hospital Basel, University of Basel, Basel, 4031, Switzerland
| | - Andrea Glutz
- Department of Biomedicine, and Clinic for Otolaryngology, Head and Neck Surgery, Hospital Basel, University of Basel, Basel, 4031, Switzerland
| | - Xunde Xian
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Joachim Herz
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Daniel Bodmer
- Department of Biomedicine, and Clinic for Otolaryngology, Head and Neck Surgery, Hospital Basel, University of Basel, Basel, 4031, Switzerland
| | - Daniel G Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, and NCCR Transcure, University of Bern, Bern, Switzerland
| | - Vesna Petkovic
- Department of Biomedicine, and Clinic for Otolaryngology, Head and Neck Surgery, Hospital Basel, University of Basel, Basel, 4031, Switzerland.
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25
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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: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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26
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Ouyang Q, Joesch-Cohen L, Mishra S, Riaz HA, Schmidt M, Morrow EM. Functional Assessment In Vivo of the Mouse Homolog of the Human Ala-9-Ser NHE6 Variant. eNeuro 2019; 6:ENEURO. [PMID: 31676550 DOI: 10.1523/ENEURO.0046-19.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [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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27
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Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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Gao AYL, Ilie A, Chang PKY, Orlowski J, McKinney RA. 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] [What about the content of this article? (0)] [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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Ieda D, Hori I, Nakamura Y, Ohashi K, Negishi Y, Hattori A, Arisaka A, Hasegawa S, Saitoh S. A novel splicing mutation in SLC9A6 in a boy with Christianson syndrome. Hum Genome Var 2019; 6:15. [PMID: 30937176 DOI: 10.1038/s41439-019-0046-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [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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Rasika S, Passemard S, Verloes A, Gressens P, El Ghouzzi V. Golgipathies in Neurodevelopment: A New View of Old Defects. Dev Neurosci 2019; 40:396-416. [PMID: 30878996 DOI: 10.1159/000497035] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 01/16/2019] [Indexed: 11/19/2022] Open
Abstract
The Golgi apparatus (GA) is involved in a whole spectrum of activities, from lipid biosynthesis and membrane secretion to the posttranslational processing and trafficking of most proteins, the control of mitosis, cell polarity, migration and morphogenesis, and diverse processes such as apoptosis, autophagy, and the stress response. In keeping with its versatility, mutations in GA proteins lead to a number of different disorders, including syndromes with multisystem involvement. Intriguingly, however, > 40% of the GA-related genes known to be associated with disease affect the central or peripheral nervous system, highlighting the critical importance of the GA for neural function. We have previously proposed the term "Golgipathies" in relation to a group of disorders in which mutations in GA proteins or their molecular partners lead to consequences for brain development, in particular postnatal-onset microcephaly (POM), white-matter defects, and intellectual disability (ID). Here, taking into account the broader role of the GA in the nervous system, we refine and enlarge this emerging concept to include other disorders whose symptoms may be indicative of altered neurodevelopmental processes, from neurogenesis to neuronal migration and the secretory function critical for the maturation of postmitotic neurons and myelination.
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Affiliation(s)
- Sowmyalakshmi Rasika
- NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,AP HP, Hôpital Robert Debré, UF de Génétique Clinique, Paris, France
| | - Sandrine Passemard
- NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,AP HP, Hôpital Robert Debré, UF de Génétique Clinique, Paris, France
| | - Alain Verloes
- NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,AP HP, Hôpital Robert Debré, UF de Génétique Clinique, Paris, France
| | - Pierre Gressens
- NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.,Centre for the Developing Brain, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, United Kingdom
| | - Vincent El Ghouzzi
- NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Sorbonne Paris Cité, Paris, France,
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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. Mol 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Ilie A, Gao AY, Boucher A, Park J, Berghuis AM, Hoffer MJ, Hilhorst-hofstee Y, Mckinney RA, Orlowski J. 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] [What about the content of this article? (0)] [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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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: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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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 2018; 165:106867. [PMID: 29772390 DOI: 10.1016/j.nlm.2018.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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Schönewolf-Greulich B, Bisgaard AM, Møller R, Dunø M, Brøndum-Nielsen K, Kaur S, Van Bergen N, Lunke S, Eggers S, Jespersgaard C, Christodoulou J, Tümer Z. Clinician’s guide to genes associated with Rett-like phenotypes-Investigation of a Danish cohort and review of the literature. Clin Genet 2018; 95:221-230. [DOI: 10.1111/cge.13153] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 10/04/2017] [Accepted: 10/05/2017] [Indexed: 12/16/2022]
Affiliation(s)
- B. Schönewolf-Greulich
- Center for Rett Syndrome, Kennedy Center, Department of Paediatrics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
| | - A-M. Bisgaard
- Center for Rett Syndrome, Kennedy Center, Department of Paediatrics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
| | - R.S. Møller
- Danish Epilepsy Centre; Dianalund Denmark
- Institute for Regional Health Services; University of Southern Denmark; Odense Denmark
| | - M. Dunø
- Department of Clinical Genetics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
| | - K. Brøndum-Nielsen
- Department of Clinical Genetics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
| | - S. Kaur
- Neurodevelopmental Genomics Research Group; Murdoch Children's Research Institute; Melbourne Australia
- Department of Paediatrics; Melbourne Medical School, University of Melbourne; Melbourne Australia
| | - N.J. Van Bergen
- Neurodevelopmental Genomics Research Group; Murdoch Children's Research Institute; Melbourne Australia
- Department of Paediatrics; Melbourne Medical School, University of Melbourne; Melbourne Australia
| | - S. Lunke
- Translational Genomics Unit; Murdoch Children’s Research Institute; Melbourne Australia
| | - S. Eggers
- Translational Genomics Unit; Murdoch Children’s Research Institute; Melbourne Australia
| | - C. Jespersgaard
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
| | - J. Christodoulou
- Neurodevelopmental Genomics Research Group; Murdoch Children's Research Institute; Melbourne Australia
- Department of Paediatrics; Melbourne Medical School, University of Melbourne; Melbourne Australia
| | - Z. Tümer
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics; Copenhagen University Hospital, Rigshospitalet; Copenhagen Denmark
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Xu M, Ouyang Q, Gong J, Pescosolido MF, Pruett BS, Mishra S, Schmidt M, Jones RN, Gamsiz Uzun ED, Lizarraga SB, Morrow EM. Mixed Neurodevelopmental and Neurodegenerative Pathology in Nhe6-Null Mouse Model of Christianson Syndrome. eNeuro 2017; 4:ENEURO. [PMID: 29349289 DOI: 10.1523/ENEURO.0388-17.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [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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Padmanabha H, Saini AG, Sahu JK, Singhi P. Syndrome of X linked intellectual disability, epilepsy, progressive brain atrophy and large head associated with SLC9A6 mutation. BMJ Case Rep 2017; 2017:bcr-2017-222050. [PMID: 29275387 DOI: 10.1136/bcr-2017-222050] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
SLC9A6 gene encodes for a sodium/hydrogen exchanger-6 protein mainly involved in endosomal trafficking and maintaining intraluminal pH. Loss of function mutations in SLC9A6 gene in children has been associated with Christianson syndrome and autism spectrum disorder. We describe a 3-year-old boy with intellectual disability, infantile-onset drug-refractory epilepsy, progressive brain atrophy and large head with a novel missense hemizygous mutation in exon 16 of the SLC9A6 gene on chromosome X. Presence of large head, early developmental regression and progressive cerebral atrophy expand the phenotypic spectrum of SLC9A6 mutations. Our case also highlights the importance of genetic testing in children with unexplained intellectual disability, epilepsy and neurodevelopmental impairments.
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Affiliation(s)
- Hansashree Padmanabha
- Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Arushi Gahlot Saini
- Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Jitendra Kumar Sahu
- Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Pratibha Singhi
- Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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Ilie A, Gao AYL, Reid J, Boucher A, McEwan C, Barrière H, Lukacs GL, McKinney RA, Orlowski J. A Christianson syndrome-linked deletion mutation (∆(287)ES(288)) in SLC9A6 disrupts recycling endosomal function and elicits neurodegeneration and cell death. Mol Neurodegener 2016; 11:63. [PMID: 27590723 PMCID: PMC5010692 DOI: 10.1186/s13024-016-0129-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 08/27/2016] [Indexed: 01/19/2023] Open
Abstract
Background Christianson Syndrome, a recently identified X-linked neurodevelopmental disorder, is caused by mutations in the human gene SLC9A6 encoding the recycling endosomal alkali cation/proton exchanger NHE6. The patients have pronounced limitations in cognitive ability, motor skills and adaptive behaviour. However, the mechanistic basis for this disorder is poorly understood as few of the more than 20 mutations identified thus far have been studied in detail. Methods Here, we examined the molecular and cellular consequences of a 6 base-pair deletion of amino acids Glu287 and Ser288 (∆ES) in the predicted seventh transmembrane helix of human NHE6 expressed in established cell lines (CHO/AP-1, HeLa and neuroblastoma SH-SY5Y) and primary cultures of mouse hippocampal neurons by measuring levels of protein expression, stability, membrane trafficking, endosomal function and cell viability. Results In the cell lines, immunoblot analyses showed that the nascent mutant protein was properly synthesized and assembled as a homodimer, but its oligosaccharide maturation and half-life were markedly reduced compared to wild-type (WT) and correlated with enhanced ubiquitination leading to both proteasomal and lysosomal degradation. Despite this instability, a measurable fraction of the transporter was correctly sorted to the plasma membrane. However, the rates of clathrin-mediated endocytosis of the ∆ES mutant as well as uptake of companion vesicular cargo, such as the ligand-bound transferrin receptor, were significantly reduced and correlated with excessive endosomal acidification. Notably, ectopic expression of ∆ES but not WT induced apoptosis when examined in AP-1 cells. Similarly, in transfected primary cultures of mouse hippocampal neurons, membrane trafficking of the ∆ES mutant was impaired and elicited marked reductions in total dendritic length, area and arborization, and triggered apoptotic cell death. Conclusions These results suggest that loss-of-function mutations in NHE6 disrupt recycling endosomal function and trafficking of cargo which ultimately leads to neuronal degeneration and cell death in Christianson Syndrome. Electronic supplementary material The online version of this article (doi:10.1186/s13024-016-0129-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Andy Y L Gao
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Jonathan Reid
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Cassandra McEwan
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Hervé Barrière
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada.
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Masurel-Paulet A, Piton A, Chancenotte S, Redin C, Thauvin-Robinet C, Henrenger Y, Minot D, Creppy A, Ruffier-Bourdet M, Thevenon J, Kuentz P, Lehalle D, Curie A, Blanchard G, Ghosn E, Bonnet M, Archimbaud-Devilliers M, Huet F, Perret O, Philip N, Mandel JL, Faivre L. A new family with anSLC9A6mutation expanding the phenotypic spectrum of Christianson syndrome. Am J Med Genet A 2016; 170:2103-10. [DOI: 10.1002/ajmg.a.37765] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 05/11/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Alice Masurel-Paulet
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
| | - Amélie Piton
- Laboratoire “Mécanismes génétiques des maladies neurodéveloppementales”; IGBMC; Illkirch France
- Laboratoire de Diagnostic génétique; CHU Strasbourg; Strasbourg France
| | - Sophie Chancenotte
- Centre Référent des Troubles du Langage et des Apprentissages; Hôpital d'Enfants; CHU Dijon; Dijon France
| | - Claire Redin
- Laboratoire “Mécanismes génétiques des maladies neurodéveloppementales”; IGBMC; Illkirch France
- Laboratoire de Diagnostic génétique; CHU Strasbourg; Strasbourg France
| | - Christel Thauvin-Robinet
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
| | - Yvan Henrenger
- Laboratoire de Diagnostic génétique; CHU Strasbourg; Strasbourg France
| | - Delphine Minot
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
| | - Audrey Creppy
- Laboratoire “Mécanismes génétiques des maladies neurodéveloppementales”; IGBMC; Illkirch France
- Laboratoire de Diagnostic génétique; CHU Strasbourg; Strasbourg France
| | - Marie Ruffier-Bourdet
- Centre Référent des Troubles du Langage et des Apprentissages; Hôpital d'Enfants; CHU Dijon; Dijon France
| | - Julien Thevenon
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
| | - Paul Kuentz
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
| | - Daphné Lehalle
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
| | - Aurore Curie
- Service de neurologie pédiatrique, Hôpital Femme Mère Enfant; Hospices Civils de Lyon; Lyon France
| | - Gaelle Blanchard
- Service de neurologie pédiatrique, Hôpital Femme Mère Enfant; Hospices Civils de Lyon; Lyon France
| | - Ezzat Ghosn
- Service de Pédiatre; Centre Hospitalier de Chalon-sur-Saône; Chalon-sur-Saône France
| | - Marlene Bonnet
- Centre Référent des Troubles du Langage et des Apprentissages; Hôpital d'Enfants; CHU Dijon; Dijon France
| | | | - Frédéric Huet
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
| | - Odile Perret
- Centre de génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs, AMU; APHM; Marseille France
| | - Nicole Philip
- Centre de génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs, AMU; APHM; Marseille France
| | - Jean-Louis Mandel
- Laboratoire “Mécanismes génétiques des maladies neurodéveloppementales”; IGBMC; Illkirch France
- Laboratoire de Diagnostic génétique; CHU Strasbourg; Strasbourg France
| | - Laurence Faivre
- Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs; Hôpital d'Enfants; CHU Dijon; Dijon France
- Fédération Hospitalo-Universitaire TRANSLAD; CHU Dijon et Université Fédérale de Bourgogne Franche Comté; Dijon France
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Patak J, Zhang-James Y, Faraone SV. Endosomal system genetics and autism spectrum disorders: A literature review. Neurosci Biobehav Rev 2016; 65:95-112. [PMID: 27048963 PMCID: PMC4866511 DOI: 10.1016/j.neubiorev.2016.03.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/25/2016] [Accepted: 03/27/2016] [Indexed: 01/01/2023]
Abstract
Autism spectrum disorders (ASDs) are a group of debilitating neurodevelopmental disorders thought to have genetic etiology, due to their high heritability. The endosomal system has become increasingly implicated in ASD pathophysiology. In an attempt to summarize the association between endosomal system genes and ASDs we performed a systematic review of the literature. We searched PubMed for relevant articles. Simons Foundation Autism Research Initiative (SFARI) gene database was used to exclude articles regarding genes with less than minimal evidence for association with ASDs. Our search retained 55 articles reviewed in two categories: genes that regulate and genes that are regulated by the endosomal system. Our review shows that the endosomal system is a novel pathway implicated in ASDs as well as other neuropsychiatric disorders. It plays a central role in aspects of cellular physiology on which neurons and glial cells are particularly reliant, due to their unique metabolic and functional demands. The system shows potential for biomarkers and pharmacological intervention and thus more research into this pathway is warranted.
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Affiliation(s)
- Jameson Patak
- Dept. of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, United States.
| | - Yanli Zhang-James
- Dept of Psychiatry, Upstate Medical University, Syracuse, NY, United States.
| | - Stephen V Faraone
- Dept. of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, United States; Dept of Psychiatry, Upstate Medical University, Syracuse, NY, United States; K.G. Jebsen Centre for Neuropsychiatric Disorders, Department of Biomedicine, University of Bergen, Bergen, Norway.
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Sinajon P, Verbaan D, So J. The expanding phenotypic spectrum of female SLC9A6 mutation carriers: a case series and review of the literature. Hum Genet 2016; 135:841-50. [DOI: 10.1007/s00439-016-1675-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 04/26/2016] [Indexed: 10/21/2022]
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Zhao H, Carney KE, Falgoust L, Pan JW, Sun D, Zhang Z. Emerging roles of Na⁺/H⁺ exchangers in epilepsy and developmental brain disorders. Prog Neurobiol 2016; 138-140:19-35. [PMID: 26965387 DOI: 10.1016/j.pneurobio.2016.02.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/03/2016] [Accepted: 02/27/2016] [Indexed: 12/15/2022]
Abstract
Epilepsy is a common central nervous system (CNS) disease characterized by recurrent transient neurological events occurring due to abnormally excessive or synchronous neuronal activity in the brain. The CNS is affected by systemic acid-base disorders, and epileptic seizures are sensitive indicators of underlying imbalances in cellular pH regulation. Na(+)/H(+) exchangers (NHEs) are a family of membrane transporter proteins actively involved in regulating intracellular and organellar pH by extruding H(+) in exchange for Na(+) influx. Altering NHE function significantly influences neuronal excitability and plays a role in epilepsy. This review gives an overview of pH regulatory mechanisms in the brain with a special focus on the NHE family and the relationship between epilepsy and dysfunction of NHE isoforms. We first discuss how cells translocate acids and bases across the membrane and establish pH homeostasis as a result of the concerted effort of enzymes and ion transporters. We focus on the specific roles of the NHE family by detailing how the loss of NHE1 in two NHE mutant mice results in enhanced neuronal excitability in these animals. Furthermore, we highlight new findings on the link between mutations of NHE6 and NHE9 and developmental brain disorders including epilepsy, autism, and attention deficit hyperactivity disorder (ADHD). These studies demonstrate the importance of NHE proteins in maintaining H(+) homeostasis and their intricate roles in the regulation of neuronal function. A better understanding of the mechanisms underlying NHE1, 6, and 9 dysfunctions in epilepsy formation may advance the development of new epilepsy treatment strategies.
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Affiliation(s)
- Hanshu Zhao
- Department of Neurology, The First Affiliated Hospital of the Harbin Medical University, Harbin, China.,Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Karen E Carney
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lindsay Falgoust
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jullie W Pan
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, PA 15213, USA
| | - Zhongling Zhang
- Department of Neurology, The First Affiliated Hospital of the Harbin Medical University, Harbin, China
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Coorg R, Weisenberg JLZ. Successful Treatment of Electrographic Status Epilepticus of Sleep With Felbamate in a Patient With SLC9A6 Mutation. Pediatr Neurol 2015; 53:527-31. [PMID: 26421989 DOI: 10.1016/j.pediatrneurol.2015.07.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 07/12/2015] [Accepted: 07/14/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND Mutations of SLC9A6 may cause an X-linked clinical syndrome first described by Christianson in 1999 in which affected males exhibited profound intellectual disability, autism, drug-resistant epilepsy, ophthalmoplegia, mild craniofacial dysmorphism, microcephaly, and ataxia. METHODS We describe a child with an SLC9A6 mutation and an electroencephalographic pattern consistent with electrographic status epilepticus of sleep. RESULTS Our patient's electrographic status epilepticus of sleep resolved after treatment with felbamate. Following treatment, he remained seizure-free but did not make significant or lasting gains in language. CONCLUSION Our report extends the clinical epilepsy phenotype in children with SLC9A6 mutations to include electrographic status epilepticus of sleep. In addition, felbamate was an effective treatment for electrographic status epilepticus of sleep in our patient.
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Affiliation(s)
- Rohini Coorg
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri; Department of Pediatrics, Baylor College of Medicine, Houston, Texas; Department of Neurology, Baylor College of Medicine, Houston, Texas.
| | - Judith L Z Weisenberg
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
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46
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Sikora J, Leddy J, Gulinello M, Walkley SU. X-linked Christianson syndrome: heterozygous female Slc9a6 knockout mice develop mosaic neuropathological changes and related behavioral abnormalities. Dis Model Mech 2015; 9:13-23. [PMID: 26515654 PMCID: PMC4728337 DOI: 10.1242/dmm.022780] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 10/25/2015] [Indexed: 01/31/2023] Open
Abstract
Christianson syndrome (CS) is an X-linked neurodevelopmental and neurological disorder characterized in males by core symptoms that include non-verbal status, intellectual disability, epilepsy, truncal ataxia, postnatal microcephaly and hyperkinesis. CS is caused by mutations in the SLC9A6 gene, which encodes a multipass transmembrane sodium (potassium)-hydrogen exchanger 6 (NHE6) protein, functional in early recycling endosomes. The extent and variability of the CS phenotype in female heterozygotes, who presumably express the wild-type and mutant SLC9A6 alleles mosaically as a result of X-chromosome inactivation (XCI), have not yet been systematically characterized. Slc9a6 knockout mice (Slc9a6 KO) were generated by insertion of the bacterial lacZ/β-galactosidase (β-Gal) reporter into exon 6 of the X-linked gene. Mutant Slc9a6 KO male mice have been shown to develop late endosomal/lysosomal dysfunction associated with glycolipid accumulation in selected neuronal populations and patterned degeneration of Purkinje cells (PCs). In heterozygous female Slc9a6 KO mice, β-Gal serves as a transcriptional/XCI reporter and thus facilitates testing of effects of mosaic expression of the mutant allele on penetrance of the abnormal phenotype. Using β-Gal, we demonstrated mosaic expression of the mutant Slc9a6 allele and mosaically distributed lysosomal glycolipid accumulation and PC pathology in the brains of heterozygous Slc9a6 KO female mice. At the behavioral level, we showed that heterozygous female mice suffer from visuospatial memory and motor coordination deficits similar to but less severe than those observed in X-chromosome hemizygous mutant males. Our studies in heterozygous Slc9a6 KO female mice provide important clues for understanding the likely phenotypic range of Christianson syndrome among females heterozygous for SLC9A6 mutations and might improve diagnostic practice and genetic counseling by helping to characterize this presumably underappreciated patient/carrier group.
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Affiliation(s)
- Jakub Sikora
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA Institute of Inherited Metabolic Disorders, Charles University in Prague - 1st Faculty of Medicine, Ke Karlovu 2, Praha 2 160 00, Czech Republic
| | - Jennifer Leddy
- Dominick P. Purpura Department 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 Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Steven U Walkley
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Gamsiz ED, Sciarra LN, Maguire AM, Pescosolido MF, van Dyck LI, Morrow EM. Discovery of Rare Mutations in Autism: Elucidating Neurodevelopmental Mechanisms. Neurotherapeutics 2015; 12:553-71. [PMID: 26105128 PMCID: PMC4489950 DOI: 10.1007/s13311-015-0363-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Autism spectrum disorder (ASD) is a group of highly genetic neurodevelopmental disorders characterized by language, social, cognitive, and behavioral abnormalities. ASD is a complex disorder with a heterogeneous etiology. The genetic architecture of autism is such that a variety of different rare mutations have been discovered, including rare monogenic conditions that involve autistic symptoms. Also, de novo copy number variants and single nucleotide variants contribute to disease susceptibility. Finally, autosomal recessive loci are contributing to our understanding of inherited factors. We will review the progress that the field has made in the discovery of these rare genetic variants in autism. We argue that mutation discovery of this sort offers an important opportunity to identify neurodevelopmental mechanisms in disease. The hope is that these mechanisms will show some degree of convergence that may be amenable to treatment intervention.
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Affiliation(s)
- Ece D. Gamsiz
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
- />Developmental Disorders Genetics Research Program, Emma Pendleton Bradley Hospital and Department of Psychiatry and Human Behavior, Brown University Medical School, Providence, RI USA
| | - Laura N. Sciarra
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
- />Neuroscience Graduate Program (NSGP), Brown University, Providence, RI USA
| | - Abbie M. Maguire
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
- />Molecular Biology, Cell Biology and Biochemistry (MCB) Graduate Training Program, Brown University, Providence, RI USA
| | - Matthew F. Pescosolido
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
- />Neuroscience Graduate Program (NSGP), Brown University, Providence, RI USA
| | - Laura I. van Dyck
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
| | - Eric M. Morrow
- />Department of Molecular Biology, Cell Biology and Biochemistry (MCB), and Institute for Brain Science, Brown University, Providence, RI USA
- />Developmental Disorders Genetics Research Program, Emma Pendleton Bradley Hospital and Department of Psychiatry and Human Behavior, Brown University Medical School, Providence, RI USA
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Hunter JM, Kiefer J, Balak CD, Jooma S, Ahearn ME, Hall JG, Baumbach-Reardon L. Review of X-linked syndromes with arthrogryposis or early contractures-aid to diagnosis and pathway identification. Am J Med Genet A 2015; 167A:931-73. [DOI: 10.1002/ajmg.a.36934] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/05/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Jesse M. Hunter
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Jeff Kiefer
- Knowledge Mining; Translational Genomics Research Institute; Phoenix Arizona
| | - Christopher D. Balak
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Sonya Jooma
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Mary Ellen Ahearn
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Judith G. Hall
- Departments of Medical Genetics and Pediatrics; University of British Columbia and BC Children's Hospital Vancouver; British Columbia Canada
| | - Lisa Baumbach-Reardon
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
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Tan CA, Topper S, Del Gaudio D, Nelakuditi V, Shchelochkov O, Nowaczyk MJM, Zeesman S, Brady L, Russell L, Meeks N, Sastry S, Arndt K, Kobiernicki F, Shaw R, Das S. Characterization of patients referred for non-specific intellectual disability testing: the importance of autosomal genes for diagnosis. Clin Genet 2015; 89:478-483. [PMID: 25693842 DOI: 10.1111/cge.12575] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 02/11/2015] [Accepted: 02/16/2015] [Indexed: 11/30/2022]
Abstract
Genetic testing for non-specific intellectual disability (ID) presents challenges in daily clinical practice. Historically, the focus of the genetic elucidation of non-specific ID has been on genes on the X chromosome, and recent research has brought attention to the growing contribution of autosomal genes. In addition, next-generation sequencing (NGS) has greatly improved the ability to simultaneously analyze multiple genetic loci, making large panel testing a practical approach to testing for non-specific ID. We performed NGS analysis of a total of 90 genes implicated in non-specific ID. The 90 genes included 56 X-linked genes and 34 autosomal genes. Pathogenic variants were identified in 11 of 52 (21%) patient samples. Nine of the eleven cases harbored mutations in autosomal genes including AP4B1, STXB1, SYNGAP1, TCF4 and UBE3A. Our mutation-positive cases provide further evidence supporting the prevalence of autosomal mutations in patients referred for non-specific ID testing and the utility of their inclusion in multi-gene panel analysis.
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Affiliation(s)
- C A Tan
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - S Topper
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - D Del Gaudio
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - V Nelakuditi
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - O Shchelochkov
- Division of Genetics, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - M J M Nowaczyk
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - S Zeesman
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - L Brady
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - L Russell
- Department of Medical Genetics, Montreal General Hospital, Montreal, QC, Canada
| | - N Meeks
- Department of Pediatrics, Section of Genetics, University of Colorado, Aurora, CO, USA
| | - S Sastry
- Division of Genetic and Metabolic Disorders, Children's Hospital of Michigan, Detroit, MI, USA
| | - K Arndt
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - F Kobiernicki
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - R Shaw
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
| | - S Das
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
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Prasad H, Rao R. The Na+/H+ exchanger NHE6 modulates endosomal pH to control processing of amyloid precursor protein in a cell culture model of Alzheimer disease. J Biol Chem 2015; 290:5311-27. [PMID: 25561733 DOI: 10.1074/jbc.m114.602219] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Early intervention may be key to safe and effective therapies in patients with Alzheimer disease. Endosomal dysfunction is an early step in neurodegeneration. Endosomes are a major site of production of Aβ peptide from the processing of amyloid precursor protein (APP) by clipping enzymes (β- and γ-secretases). The β-secretase enzyme BACE1 requires acidic lumen pH for optimum function, and acid pH promotes Aβ aggregation. The Na(+)/H(+) exchanger NHE6 provides a leak pathway for protons, limiting luminal acidification by proton pumps. Like APP, NHE6 expression was induced upon differentiation of SH-SY5Y neuroblastoma cells and localized to an endosomal compartment. Therefore, we investigated whether NHE6 expression altered APP localization and processing in a stably transfected cell culture model of human APP expression. We show that co-expression with NHE6 or treatment with the Na(+)/H(+) ionophore monensin shifted APP away from the trans-Golgi network into early and recycling endosomes in HEK293 cells. NHE6 alkalinized the endosomal lumen, similar to monensin, and significantly attenuated APP processing and Aβ secretion. In contrast, Aβ production was elevated upon NHE6 knockdown. We show that NHE6 transcript and protein levels are lowered in Alzheimer brains relative to control. These findings, taken together with emerging genetic evidence linking endosomal Na(+)/H(+) exchangers with Alzheimer disease, suggest that proton leak pathways may regulate Aβ generation and contribute to disease etiology.
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Affiliation(s)
- Hari Prasad
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Rajini Rao
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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