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Gao AYL, Inglebert Y, Shi R, Ilie A, Popic J, Mustian J, Sonenberg N, Orlowski J, McKinney RA. Impaired hippocampal plasticity associated with loss of recycling endosomal SLC9A6/NHE6 is ameliorated by the TrkB agonist 7,8-dihydroxyflavone. Biochim Biophys Acta Mol Basis Dis 2024; 1871:167529. [PMID: 39341363 DOI: 10.1016/j.bbadis.2024.167529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Revised: 08/31/2024] [Accepted: 09/24/2024] [Indexed: 10/01/2024]
Abstract
Proper maintenance of intracellular vesicular pH is essential for cargo trafficking during synaptic function and plasticity. Mutations in the SLC9A6 gene encoding the recycling endosomal pH regulator (Na+, K+)/H+ exchanger isoform 6 (NHE6) are causal for Christianson syndrome (CS), a severe form of X-linked intellectual disability. NHE6 expression is also downregulated in other neurodevelopmental and neurodegenerative disorders, such as autism spectrum disorder and Alzheimer's disease, suggesting its dysfunction could contribute more broadly to the pathophysiology of other neurological conditions. To understand how ablation of NHE6 function leads to severe learning impairments, we assessed synaptic structure, function, and cellular mechanisms of learning in a novel line of Nhe6 knockout (KO) mice expressing a plasma membrane-tethered green fluorescent protein within hippocampal neurons. We uncovered significant reductions in dendritic spines density, AMPA receptor (AMPAR) expression, and AMPAR-mediated neurotransmission in CA1 pyramidal neurons. The neurons also failed to undergo functional and structural enhancement during long-term potentiation (LTP). Significantly, the selective TrkB agonist 7,8-dihydroxyflavone restored spine density as well as functional and structural LTP in KO neurons. TrkB activation thus may act as a potential clinical intervention to ameliorate cognitive deficits in CS and other neurodegenerative disorders.
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Affiliation(s)
- Andy Y L Gao
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Canada
| | - Yanis Inglebert
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Canada
| | - Roy Shi
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Canada
| | - Alina Ilie
- Department of Physiology, McGill University, Montreal, Canada
| | - Jelena Popic
- Department of Biochemistry, McGill University, Montreal, Canada
| | - Jamie Mustian
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Canada
| | - R Anne McKinney
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Canada.
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2
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O'Connor M, Qiao H, Odamah K, Cerdeira PC, Man HY. Heterozygous Nexmif female mice demonstrate mosaic NEXMIF expression, autism-like behaviors, and abnormalities in dendritic arborization and synaptogenesis. Heliyon 2024; 10:e24703. [PMID: 38322873 PMCID: PMC10844029 DOI: 10.1016/j.heliyon.2024.e24703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 11/28/2023] [Accepted: 01/12/2024] [Indexed: 02/08/2024] Open
Abstract
Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a strong genetic basis. ASDs are commonly characterized by impairments in language, restrictive and repetitive behaviors, and deficits in social interactions. Although ASD is a highly heterogeneous disease with many different genes implicated in its etiology, many ASD-associated genes converge on common cellular defects, such as aberrant neuronal morphology and synapse dysregulation. Our previous work revealed that, in mice, complete loss of the ASD-associated X-linked gene NEXMIF results in a reduction in dendritic complexity, a decrease in spine and synapse density, altered synaptic transmission, and ASD-like behaviors. Interestingly, human females of NEXMIF haploinsufficiency have recently been reported to demonstrate autistic features; however, the cellular and molecular basis for this haploinsufficiency-caused ASD remains unclear. Here we report that in the brains of Nexmif± female mice, NEXMIF shows a mosaic pattern in its expression in neurons. Heterozygous female mice demonstrate behavioral impairments similar to those of knockout male mice. In the mosaic mixture of neurons from Nexmif± mice, cells that lack NEXMIF have impairments in dendritic arborization and spine development. Remarkably, the NEXMIF-expressing neurons from Nexmif± mice also demonstrate similar defects in dendritic growth and spine formation. These findings establish a novel mouse model of NEXMIF haploinsufficiency and provide new insights into the pathogenesis of NEXMIF-dependent ASD.
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Affiliation(s)
- Margaret O'Connor
- Department of Biology, Boston University, 5 Cummington Mall, Boston, MA 02215, USA
| | - Hui Qiao
- Department of Biology, Boston University, 5 Cummington Mall, Boston, MA 02215, USA
| | - KathrynAnn Odamah
- Department of Biology, Boston University, 5 Cummington Mall, Boston, MA 02215, USA
| | | | - Heng-Ye Man
- Department of Biology, Boston University, 5 Cummington Mall, Boston, MA 02215, USA
- Department of Pharmacology, Physiology & Biophysics, Boston University School of Medicine, 72 East Concord St., Boston, MA 02118, USA
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Ave, Boston, MA 02215, USA
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3
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Figueroa KP, Anderson CJ, Paul S, Dansithong W, Gandelman M, Scoles DR, Pulst SM. Slc9a6 mutation causes Purkinje cell loss and ataxia in the shaker rat. Hum Mol Genet 2023; 32:1647-1659. [PMID: 36621975 PMCID: PMC10162436 DOI: 10.1093/hmg/ddad004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 12/29/2022] [Accepted: 01/05/2023] [Indexed: 01/10/2023] Open
Abstract
The shaker rat carries a naturally occurring mutation leading to progressive ataxia characterized by Purkinje cell (PC) loss. We previously reported on fine-mapping the shaker locus to the long arm of the rat X chromosome. In this work, we sought to identify the mutated gene underlying the shaker phenotype and confirm its identity by functional complementation. We fine-mapped the candidate region and analyzed cerebellar transcriptomes, identifying a XM_217630.9 (Slc9a6):c.[191_195delinsA] variant in the Slc9a6 gene that segregated with disease. We generated an adeno-associated virus (AAV) targeting Slc9a6 expression to PCs using the mouse L7-6 (L7) promoter. We administered the AAV prior to the onset of PC degeneration through intracerebroventricular injection and found that it reduced the shaker motor, molecular and cellular phenotypes. Therefore, Slc9a6 is mutated in shaker and AAV-based gene therapy may be a viable therapeutic strategy for Christianson syndrome, also caused by Slc9a6 mutation.
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Affiliation(s)
- Karla P Figueroa
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Collin J Anderson
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
- School of Medical Sciences, University of Sydney, Camperdown NSW 2006, Australia
- School of Biomedical Engineering University of Sydney, Darlington NSW 2008, Australia
| | - Sharan Paul
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Warunee Dansithong
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Mandi Gandelman
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Daniel R Scoles
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Stefan M Pulst
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
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4
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Dong Y, Lian R, Jin L, Zhao S, Tao W, Wang L, Li M, Jia T, Chen X, Cao S. Clinical and genetic analysis of Christianson syndrome caused by variant of SLC9A6: case report and literature review. Front Neurol 2023; 14:1152696. [PMID: 37213903 PMCID: PMC10196350 DOI: 10.3389/fneur.2023.1152696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 04/18/2023] [Indexed: 05/23/2023] Open
Abstract
Background Intellectual disability, X-linked, syndromic, Christianson type (MRXSCH, OMIM: 300243)-known as Christianson syndrome (CS)-is characterized by microcephaly, epilepsy, ataxia, and absence of verbal language ability. CS is attributed to mutations in the solute carrier family 9 member A6 gene (SLC9A6). Materials and methods This study reports the case of a boy 1 year and 3 months of age who was diagnosed with CS in our department. Genetic etiology was determined by whole-exome sequencing, and a minigene splicing assay was used to verify whether the mutation affected splicing. A literature review of CS cases was conducted and the clinical and genetic features were summarized. Results The main clinical manifestations of CS include seizures, developmental regression, and exceptional facial features. Whole-exome sequencing revealed a de novo splice variant in intron 11 (c.1366 + 1G > C) of SLC9A6. The mutation produced two abnormal mRNA products (verified by a minigene splicing assay), resulting in the formation of truncated protein. A total of 95 CS cases were identified in the literature, with various symptoms, such as delayed intellectual development (95/95, 100.00%), epilepsy (87/88, 98.86%), and absent verbal language (75/83, 90.36%). At least 50 pathogenic variants of SLC9A6 have been identified, with the highest frequency observed in exon 12. Conclusion Our patient is the first case with the c.1366 + 1G > C variant of SLC9A6 in CS. The summary of known cases can serve as a reference for analyzing the mutation spectrum and pathogenesis of CS.
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Affiliation(s)
- Yan Dong
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- Henan Key Laboratory of Child Brain Injury and Henan Pediatric Clinical Research Center, The Third Affiliated Hospital and Institute of Neuroscience, Zhengzhou, China
- *Correspondence: Yan Dong,
| | - Ruofei Lian
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Liang Jin
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shichao Zhao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Wenpeng Tao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Lijun Wang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Mengchun Li
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Tianming Jia
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Xuejing Chen
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shushi Cao
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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Gao AYL, Lourdin-De Filippis E, Orlowski J, McKinney RA. Roles of Endomembrane Alkali Cation/Proton Exchangers in Synaptic Function and Neurodevelopmental Disorders. Front Physiol 2022; 13:892196. [PMID: 35547574 PMCID: PMC9081726 DOI: 10.3389/fphys.2022.892196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 03/30/2022] [Indexed: 12/25/2022] Open
Abstract
Endomembrane alkali cation (Na+, K+)/proton (H+) exchangers (eNHEs) are increasingly associated with neurological disorders. These eNHEs play integral roles in regulating the luminal pH, processing, and trafficking of cargo along the secretory (Golgi and post-Golgi vesicles) and endocytic (early, recycling, and late endosomes) pathways, essential regulatory processes vital for neuronal development and plasticity. Given the complex morphology and compartmentalization of multipolar neurons, the contribution of eNHEs in maintaining optimal pH homeostasis and cargo trafficking is especially significant during periods of structural and functional development and remodeling. While the importance of eNHEs has been demonstrated in a variety of non-neuronal cell types, their involvement in neuronal function is less well understood. In this review, we will discuss their emerging roles in excitatory synaptic function, particularly as it pertains to cellular learning and remodeling. We will also explore their connections to neurodevelopmental conditions, including intellectual disability, autism, and attention deficit hyperactivity disorders.
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Affiliation(s)
- Andy Y L Gao
- Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.,Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
| | | | - John Orlowski
- Department of Physiology, McGill University, Montreal, QC, Canada
| | - R Anne McKinney
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
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6
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Loss of Christianson Syndrome Na +/H + Exchanger 6 (NHE6) Causes Abnormal Endosome Maturation and Trafficking Underlying Lysosome Dysfunction in Neurons. J Neurosci 2021; 41:9235-9256. [PMID: 34526390 PMCID: PMC8570832 DOI: 10.1523/jneurosci.1244-20.2021] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/05/2021] [Accepted: 08/07/2021] [Indexed: 01/08/2023] Open
Abstract
Loss-of-function mutations in endosomal Na+/H+ exchanger 6 (NHE6) cause the X-linked neurologic disorder Christianson syndrome. Patients exhibit symptoms associated with both neurodevelopmental and neurodegenerative abnormalities. While loss of NHE6 has been shown to overacidify the endosome lumen, and is associated with endolysosome neuropathology, NHE6-mediated mechanisms in endosome trafficking and lysosome function have been understudied. Here, we show that NHE6-null mouse neurons demonstrate worsening lysosome function with time in culture, likely as a result of defective endosome trafficking. NHE6-null neurons exhibit overall reduced lysosomal proteolysis despite overacidification of the endosome and lysosome lumen. Akin to Nhx1 mutants in Saccharomyces cerevisiae, we observe decreased endosome-lysosome fusion in NHE6-null neurons. Also, we find premature activation of pH-dependent cathepsin D (CatD) in endosomes. While active CatD is increased in endosomes, CatD activation and CatD protein levels are reduced in the lysosome. Protein levels of another mannose 6-phosphate receptor (M6PR)-dependent enzyme, β-N-acetylglucosaminidase, were also decreased in lysosomes of NHE6-null neurons. M6PRs accumulate in late endosomes, suggesting defective M6PR recycling and retromer function in NHE6-null neurons. Finally, coincident with decreased endosome-lysosome fusion, using total internal reflection fluorescence, we also find a prominent increase in fusion between endosomal multivesicular bodies and the plasma membrane, indicating enhanced exosome secretion from NHE6-null neurons. In summary, in addition to overacidification of endosomes and lysosomes, loss of NHE6 leads to defects in endosome maturation and trafficking, including enhanced exosome release, contributing to lysosome deficiency and potentially leading to neurodegenerative disease. SIGNIFICANCE STATEMENT Loss-of-function mutations in the endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome, an X-linked neurologic disorder. Loss of NHE6 has been shown to overacidify endosomes; however, endosome trafficking mechanisms have been understudied, and the mechanisms leading to neurodegeneration are largely unknown. In NHE6-null mouse neurons in vitro, we find worsening lysosome function with days in culture. Notably, pH-dependent lysosome enzymes, such as cathepsin D, have reduced activity in lysosomes yet increased, precocious activity in endosomes in NHE6-null neurons. Further, endosomes show reduced fusion to lysosomes, and increased fusion to the plasma membrane with increased exosome release. This study identifies new mechanisms involving defective endosome maturation and trafficking that impair lysosome function in Christianson syndrome, likely contributing to neurodegeneration.
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7
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Ilie A, Boucher A, Park J, Berghuis AM, McKinney RA, Orlowski J. Assorted dysfunctions of endosomal alkali cation/proton exchanger SLC9A6 variants linked to Christianson syndrome. J Biol Chem 2020; 295:7075-7095. [PMID: 32277048 PMCID: PMC7242699 DOI: 10.1074/jbc.ra120.012614] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Genetic screening has identified numerous variants of the endosomal solute carrier family 9 member A6 (SLC9A6)/(Na+,K+)/H+ exchanger 6 (NHE6) gene that cause Christianson syndrome, a debilitating X-linked developmental disorder associated with a range of neurological, somatic, and behavioral symptoms. Many of these variants cause complete loss of NHE6 expression, but how subtler missense substitutions or nonsense mutations that partially truncate its C-terminal cytoplasmic regulatory domain impair NHE6 activity and endosomal function are poorly understood. Here, we describe the molecular and cellular consequences of six unique mutations located in the N-terminal cytoplasmic segment (A9S), the membrane ion translocation domain (L188P and G383D), and the C-terminal regulatory domain (E547*, R568Q, and W570*) of human NHE6 that purportedly cause disease. Using a heterologous NHE6-deficient cell expression system, we show that the biochemical, catalytic, and cellular properties of the A9S and R568Q variants were largely indistinguishable from those of the WT transporter, which obscured their disease significance. By contrast, the L188P, G383D, E547*, and W570* mutants exhibited variable deficiencies in biosynthetic post-translational maturation, membrane sorting, pH homeostasis in recycling endosomes, and cargo trafficking, and they also triggered apoptosis. These findings broaden our understanding of the molecular dysfunctions of distinct NHE6 variants associated with Christianson syndrome.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Jaeok Park
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada
| | | | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
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8
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Kerner-Rossi M, Gulinello M, Walkley S, Dobrenis K. Pathobiology of Christianson syndrome: Linking disrupted endosomal-lysosomal function with intellectual disability and sensory impairments. Neurobiol Learn Mem 2019; 165:106867. [PMID: 29772390 PMCID: PMC6235725 DOI: 10.1016/j.nlm.2018.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 05/04/2018] [Accepted: 05/12/2018] [Indexed: 11/18/2022]
Abstract
Christianson syndrome (CS) is a recently described rare neurogenetic disorder presenting early in life with a broad range of neurological symptoms, including severe intellectual disability with nonverbal status, hyperactivity, epilepsy, and progressive ataxia due to cerebellar atrophy. CS is due to loss-of-function mutations in SLC9A6, encoding NHE6, a sodium-hydrogen exchanger involved in the regulation of early endosomal pH. Here we review what is currently known about the neuropathogenesis of CS, based on insights from experimental models, which to date have focused on mechanisms that affect the CNS, specifically the brain. In addition, parental reports of sensory disturbances in their children with CS, including an apparent insensitivity to pain, led us to explore sensory function and related neuropathology in Slc9a6 KO mice. We present new data showing sensory deficits in Slc9a6 KO mice, which had reduced behavioral responses to noxious thermal and mechanical stimuli (Hargreaves and Von Frey assays, respectively) compared to wild type (WT) littermates. Immunohistochemical and ultrastructural analysis of the spinal cord and peripheral nervous system revealed intracellular accumulation of the glycosphingolipid GM2 ganglioside in KO but not WT mice. This cellular storage phenotype was most abundant in neurons of lamina I-II of the dorsal horn, a major relay site in the processing of painful stimuli. Spinal cords of KO mice also exhibited changes in astroglial and microglial populations throughout the gray matter suggestive of a neuroinflammatory process. Our findings establish the Slc9a6 KO mouse as a relevant tool for studying the sensory deficits in CS, and highlight selective vulnerabilities in relevant cell populations that may contribute to this phenotype. How NHE6 loss of function leads to such a multifaceted neurological syndrome is still undefined, and it is likely that NHE6 is involved with many cellular processes critical to normal nervous system development and function. In addition, the sensory issues exhibited by Slc9a6 KO mice, in combination with our neuropathological findings, are consistent with NHE6 loss of function impacting the entire nervous system. Sensory dysfunction in intellectually disabled individuals is challenging to assess and may impair patient safety and quality of life. Further mechanistic studies of the neurological impairments underlying CS and other genetic intellectual disability disorders must also take into account mechanisms affecting broader nervous system function in order to understand the full range of associated disabilities.
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Affiliation(s)
- Mallory Kerner-Rossi
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Maria Gulinello
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA; IDDRC Behavioral Core Facility, Neuroscience Department, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Steven Walkley
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Kostantin Dobrenis
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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9
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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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10
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Pescosolido MF, Kavanaugh BC, Pochet N, Schmidt M, Jerskey BA, Rogg JM, De Jager PL, Young-Pearse TL, Liu JS, Morrow EM. Complex Neurological Phenotype in Female Carriers of NHE6 Mutations. MOLECULAR NEUROPSYCHIATRY 2019; 5:98-108. [PMID: 31192222 DOI: 10.1159/000496341] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022]
Abstract
Mutations in NHE6 (also termed SLC9A6) cause the X-linked neurological disorder Christianson syndrome (CS) in males. The purpose of this study was to examine the phenotypic spectrum of female carriers of NHE6 mutations. Twenty female carriers from 9 pedigrees were enrolled, ranging from approximately age 2 to 65. A subset of female carriers was assessed using standardized neuropsychological measures. Also, the association of NHE6 expression with markers of brain age was evaluated using 740 participants in the Religious Orders Study (ROS) and Rush Memory and Aging Project (MAP). A majority, but not all, female carriers demonstrated a deficit in at least one neurocognitive domain (85%). A recognizable neuropsychological profile emerged, revealing impairments in visuospatial function, attention, and executive function. Common neuropsychiatric diagnoses included: intellectual disability/developmental delay (20%), learning difficulties (31%), speech/language delays (30%), and attention-deficit/hyperactivity disorder (20%). Notable neurological diagnoses in aging CS female carriers include corticobasal degeneration and atypical parkinsonism. In postmortem brains from the ROS/MAP dataset of normal and pathological aging, decreased NHE6 expression was correlated with greater tau deposition. Our study provides an examination of the phenotypic range in female carriers of NHE6 mutations. The findings indicate that NHE6-related disease in females represents a new neurogenetic condition.
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Affiliation(s)
- Matthew F Pescosolido
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Brian C Kavanaugh
- Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Nathalie Pochet
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA.,Cell Circuits Program, Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, Massachusetts, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
| | - Beth A Jerskey
- Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA
| | - Jeffrey M Rogg
- Department of Diagnostic Imaging, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Philip L De Jager
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA.,Cell Circuits Program, Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, Massachusetts, USA
| | - Tracy L Young-Pearse
- Ann Romney Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Judy S Liu
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Department of Neurology, Rhode Island Hospital, Providence, Rhode Island, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Developmental Disorders Genetics Research Program, Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University and Emma Pendleton Bradley Hospital, East Providence, Rhode Island, USA.,Hassenfeld Child Health Innovation Institute, Brown University, Providence, Rhode Island, USA
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11
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A potential gain-of-function variant of SLC9A6 leads to endosomal alkalinization and neuronal atrophy associated with Christianson Syndrome. Neurobiol Dis 2019; 121:187-204. [DOI: 10.1016/j.nbd.2018.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 09/18/2018] [Accepted: 10/03/2018] [Indexed: 11/24/2022] Open
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12
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Mixed Neurodevelopmental and Neurodegenerative Pathology in Nhe6-Null Mouse Model of Christianson Syndrome. eNeuro 2018; 4:eN-NWR-0388-17. [PMID: 29349289 PMCID: PMC5771691 DOI: 10.1523/eneuro.0388-17.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/12/2017] [Accepted: 12/17/2017] [Indexed: 12/20/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked disorder resulting from loss-of-function mutations in SLC9A6, which encodes the endosomal Na+/H+ exchanger 6 (NHE6). Symptoms include early developmental delay, seizures, intellectual disability, nonverbal status, autistic features, postnatal microcephaly, and progressive ataxia. Neuronal development is impaired in CS, involving defects in neuronal arborization and synaptogenesis, likely underlying diminished brain growth postnatally. In addition to neurodevelopmental defects, some reports have supported neurodegenerative pathology in CS with age. The objective of this study was to determine the nature of progressive changes in the postnatal brain in Nhe6-null mice. We examined the trajectories of brain growth and atrophy in mutant mice from birth until very old age (2 yr). We report trajectories of volume changes in the mutant that likely reflect both brain undergrowth as well as tissue loss. Reductions in volume are first apparent at 2 mo, particularly in the cerebellum, which demonstrates progressive loss of Purkinje cells (PCs). We report PC loss in two distinct Nhe6-null mouse models. More widespread reductions in tissue volumes, namely, in the hippocampus, striatum, and cortex, become apparent after 2 mo, largely reflecting delays in growth with more limited tissue losses with aging. Also, we identify pronounced glial responses, particularly in major fiber tracts such as the corpus callosum, where the density of activated astrocytes and microglia are substantially increased. The prominence of the glial response in axonal tracts suggests a primary axonopathy. Importantly, therefore, our data support both neurodevelopmental and degenerative mechanisms in the pathobiology of CS.
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13
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Ratnu VS, Emami MR, Bredy TW. Genetic and epigenetic factors underlying sex differences in the regulation of gene expression in the brain. J Neurosci Res 2017; 95:301-310. [PMID: 27870402 DOI: 10.1002/jnr.23886] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/13/2016] [Accepted: 07/25/2016] [Indexed: 12/14/2022]
Abstract
There are inherent biological differences between males and females that contribute to sex differences in brain function and to many sex-specific illnesses and disorders. Traditionally, it has been thought that such differences are due largely to hormonal regulation; however, there are also genetic and epigenetic effects caused by the inheritance and unequal dosage of genes located on the X and Y chromosomes. Here we discuss the evidence in favor of a genetic and epigenetic basis for sexually dimorphic behavior, as a consequence of underlying differences in the regulation of genes that drive brain function. A better understanding of sex-specific molecular processes in the brain will provide further insight for the development of novel therapeutic approaches for the treatment of neuropsychiatric disorders characterized by sex differences. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Vikram S Ratnu
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Michael R Emami
- Department of Neurobiology and Behavior, University of California, Irvine, California
| | - Timothy W Bredy
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia.,Department of Neurobiology and Behavior, University of California, Irvine, California
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14
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Sikora J, Dworski S, Jones EE, Kamani MA, Micsenyi MC, Sawada T, Le Faouder P, Bertrand-Michel J, Dupuy A, Dunn CK, Xuan ICY, Casas J, Fabrias G, Hampson DR, Levade T, Drake RR, Medin JA, Walkley SU. Acid Ceramidase Deficiency in Mice Results in a Broad Range of Central Nervous System Abnormalities. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:864-883. [PMID: 28342444 DOI: 10.1016/j.ajpath.2016.12.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 12/02/2016] [Accepted: 12/08/2016] [Indexed: 12/30/2022]
Abstract
Farber disease is a rare autosomal recessive disorder caused by acid ceramidase deficiency that usually presents as early-onset progressive visceral and neurologic disease. To understand the neurologic abnormality, we investigated behavioral, biochemical, and cellular abnormalities in the central nervous system of Asah1P361R/P361R mice, which serve as a model of Farber disease. Behaviorally, the mutant mice had reduced voluntary locomotion and exploration, increased thigmotaxis, abnormal spectra of basic behavioral activities, impaired muscle grip strength, and defects in motor coordination. A few mutant mice developed hydrocephalus. Mass spectrometry revealed elevations of ceramides, hydroxy-ceramides, dihydroceramides, sphingosine, dihexosylceramides, and monosialodihexosylganglioside in the brain. The highest accumulation was in hydroxy-ceramides. Storage compound distribution was analyzed by mass spectrometry imaging and morphologic analyses and revealed involvement of a wide range of central nervous system cell types (eg, neurons, endothelial cells, and choroid plexus cells), most notably microglia and/or macrophages. Coalescing and mostly perivascular granuloma-like accumulations of storage-laden CD68+ microglia and/or macrophages were seen as early as 3 weeks of age and located preferentially in white matter, periventricular zones, and meninges. Neurodegeneration was also evident in specific cerebral areas in late disease. Overall, our central nervous system studies in Asah1P361R/P361R mice substantially extend the understanding of human Farber disease and suggest that this model can be used to advance therapeutic approaches for this currently untreatable disorder.
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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, New York; Institute of Inherited Metabolic Disorders, Charles University, 1st Faculty of Medicine, Prague, Czech Republic; Institute of Pathology, Charles University, 1st Faculty of Medicine, Prague, Czech Republic
| | - Shaalee Dworski
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - E Ellen Jones
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina
| | | | - Matthew C Micsenyi
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, New York
| | - Tomo Sawada
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, New York
| | - Pauline Le Faouder
- MetaToul-Lipidomic Facility-MetaboHUB, INSERM UMR1048, Institute of Cardiovascular and Metabolic Diseases, Université Paul Sabatier-Toulouse III, Toulouse, France
| | - Justine Bertrand-Michel
- MetaToul-Lipidomic Facility-MetaboHUB, INSERM UMR1048, Institute of Cardiovascular and Metabolic Diseases, Université Paul Sabatier-Toulouse III, Toulouse, France
| | - Aude Dupuy
- MetaToul-Lipidomic Facility-MetaboHUB, INSERM UMR1048, Institute of Cardiovascular and Metabolic Diseases, Université Paul Sabatier-Toulouse III, Toulouse, France
| | | | - Ingrid Cong Yang Xuan
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Josefina Casas
- Research Unit on Bioactive Molecules, Department of Biomedicinal Chemistry, Institute for Advanced Chemistry of Catalonia, Spanish National Research Council, Barcelona, Spain
| | - Gemma Fabrias
- Research Unit on Bioactive Molecules, Department of Biomedicinal Chemistry, Institute for Advanced Chemistry of Catalonia, Spanish National Research Council, Barcelona, Spain
| | - David R Hampson
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Thierry Levade
- INSERM UMR1037, Cancer Research Center of Toulouse, Universite Toulouse III Paul-Sabatier, Toulouse, France; Metabolic Biochemistry Laboratory, Federative Institute of Biology, Centre Hospitalier Universitaire de Toulouse, Toulouse, France
| | - Richard R Drake
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, South Carolina
| | - Jeffrey A Medin
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada; University Health Network, Toronto, Ontario, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Medical College of Wisconsin, Milwaukee, Wisconsin.
| | - Steven U Walkley
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, New York.
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15
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Hong SY, Chou IC, Lin WD, Tsai FJ. A case of Pitt-Hopkins syndrome presented with Angelman-like syndromic phenotypes. Biomedicine (Taipei) 2016; 6:25. [PMID: 27864810 PMCID: PMC5147553 DOI: 10.7603/s40681-016-0025-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 08/29/2016] [Indexed: 11/29/2022] Open
Abstract
Pitt-Hopkins syndrome (PTHS), caused by a TCF4 gene mutation, is a condition characterized by intellectual disability and developmental delay, breathing anomalies, epilepsy, and distinctive facial dysmorphism [1]. Its diverse clinical appearance causes pediatricians to confuse it with Angelman syndrome, which is considered one of the family members of Angelman-like syndrome. Herein, we report on a 4 y/o boy with PTHS and discuss its similarities and differences with Angelman syndrome. In doing so we hope to provide a feasible pathway to diagnose rare diseases, especially Angelman-like syndrome.
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Affiliation(s)
- Syuan-Yu Hong
- Department of Pediatrics, Children's Hospital, China Medical University Hospital, Taichung, 404, Taiwan
| | - I-Ching Chou
- Department of Pediatrics, Children's Hospital, China Medical University Hospital, Taichung, 404, Taiwan.,Department of Medical Research, China Medical University and Hospital, Taichung, 404, Taiwan
| | - Wei-De Lin
- Department of Medical Research, China Medical University and Hospital, Taichung, 404, Taiwan.,School of Post-baccalaureate Chinese Medicine, China Medical University, Taichung, 404, Taiwan
| | - Fuu-Jen Tsai
- Department of Pediatrics, Children's Hospital, China Medical University Hospital, Taichung, 404, Taiwan. .,Department of Medical Research, China Medical University and Hospital, Taichung, 404, Taiwan. .,Department of Pediatrics, China Medical University Hospital, No. 2 Yuh-Der Road, Taichung, 404, Taiwan.
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16
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 04/26/2016] [Indexed: 10/21/2022]
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