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Rudaks LI, Yeow D, Ng K, Deveson IW, Kennerson ML, Kumar KR. An Update on the Adult-Onset Hereditary Cerebellar Ataxias: Novel Genetic Causes and New Diagnostic Approaches. CEREBELLUM (LONDON, ENGLAND) 2024:10.1007/s12311-024-01703-z. [PMID: 38760634 DOI: 10.1007/s12311-024-01703-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/07/2024] [Indexed: 05/19/2024]
Abstract
The hereditary cerebellar ataxias (HCAs) are rare, progressive neurologic disorders caused by variants in many different genes. Inheritance may follow autosomal dominant, autosomal recessive, X-linked or mitochondrial patterns. The list of genes associated with adult-onset cerebellar ataxia is continuously growing, with several new genes discovered in the last few years. This includes short-tandem repeat (STR) expansions in RFC1, causing cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS), FGF14-GAA causing spinocerebellar ataxia type 27B (SCA27B), and THAP11. In addition, the genetic basis for SCA4, has recently been identified as a STR expansion in ZFHX3. Given the large and growing number of genes, and different gene variant types, the approach to diagnostic testing for adult-onset HCA can be complex. Testing methods include targeted evaluation of STR expansions (e.g. SCAs, Friedreich ataxia, fragile X-associated tremor/ataxia syndrome, dentatorubral-pallidoluysian atrophy), next generation sequencing for conventional variants, which may include targeted gene panels, whole exome, or whole genome sequencing, followed by various potential additional tests. This review proposes a diagnostic approach for clinical testing, highlights the challenges with current testing technologies, and discusses future advances which may overcome these limitations. Implementing long-read sequencing has the potential to transform the diagnostic approach in HCA, with the overall aim to improve the diagnostic yield.
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Affiliation(s)
- Laura Ivete Rudaks
- Molecular Medicine Laboratory and Neurology Department, Concord Repatriation General Hospital, Sydney, Australia.
- Faculty of Medicine and Health, The University of Sydney, Sydney, Australia.
- Genomics and Inherited Disease Program, The Garvan Institute of Medical Research, Sydney, Australia.
- Clinical Genetics Unit, Royal North Shore Hospital, Sydney, Australia.
| | - Dennis Yeow
- Molecular Medicine Laboratory and Neurology Department, Concord Repatriation General Hospital, Sydney, Australia
- Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
- Genomics and Inherited Disease Program, The Garvan Institute of Medical Research, Sydney, Australia
- Neurodegenerative Service, Prince of Wales Hospital, Sydney, Australia
- Neuroscience Research Australia, Sydney, Australia
| | - Karl Ng
- Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
- Neurology Department, Royal North Shore Hospital, Sydney, Australia
| | - Ira W Deveson
- Genomics and Inherited Disease Program, The Garvan Institute of Medical Research, Sydney, Australia
- Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Marina L Kennerson
- Molecular Medicine Laboratory and Neurology Department, Concord Repatriation General Hospital, Sydney, Australia
- Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
- The Northcott Neuroscience Laboratory, ANZAC Research Institute, Sydney Local Health District, Sydney, Australia
| | - Kishore Raj Kumar
- Molecular Medicine Laboratory and Neurology Department, Concord Repatriation General Hospital, Sydney, Australia
- Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
- Genomics and Inherited Disease Program, The Garvan Institute of Medical Research, Sydney, Australia
- Faculty of Medicine, University of New South Wales, Sydney, Australia
- Faculty of Medicine, St Vincent's Healthcare Campus, UNSW Sydney, Sydney, Australia
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Felício D, Santos M. Spinocerebellar ataxia type 11 (SCA11): TTBK2 variants, functions and associated disease mechanisms. CEREBELLUM (LONDON, ENGLAND) 2024; 23:678-687. [PMID: 36892783 PMCID: PMC10951003 DOI: 10.1007/s12311-023-01540-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/02/2023] [Indexed: 03/10/2023]
Abstract
Spinocerebellar ataxia type 11 (SCA11) is a rare type of autosomal dominant cerebellar ataxia, mainly characterized by progressive cerebellar ataxia, abnormal eye signs and dysarthria. SCA11 is caused by variants in TTBK2, which encodes tau tubulin kinase 2 (TTBK2) protein. Only a few families with SCA11 were described to date, all harbouring small deletions or insertions that result in frameshifts and truncated TTBK2 proteins. In addition, TTBK2 missense variants were also reported but they were either benign or still needed functional validation to ascertain their pathogenic potential in SCA11. The mechanisms behind cerebellar neurodegeneration mediated by TTBK2 pathogenic alleles are not clearly established. There is only one neuropathological report and a few functional studies in cell or animal models published to date. Moreover, it is still unclear whether the disease is caused by TTBK2 haploinsufficiency of by a dominant negative effect of TTBK2 truncated forms on the normal allele. Some studies point to a lack of kinase activity and mislocalization of mutated TTBK2, while others reported a disruption of normal TTBK2 function caused by SCA11 alleles, particularly during ciliogenesis. Although TTBK2 has a proven function in cilia formation, the phenotype caused by heterozygous TTBK2 truncating variants are not clearly typical of ciliopathies. Thus, other cellular mechanisms may explain the phenotype seen in SCA11. Neurotoxicity caused by impaired TTBK2 kinase activity against known neuronal targets, such as tau, TDP-43, neurotransmitter receptors or transporters, may contribute to neurodegeneration in SCA11.
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Affiliation(s)
- Daniela Felício
- UnIGENe, IBMC-Institute for Molecular and Cell Biology, i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135, Porto, Portugal
- ICBAS, Instituto Ciências Biomédicas Abel Salazar, Universidade do Porto, 4050-313, Porto, Portugal
| | - Mariana Santos
- UnIGENe, IBMC-Institute for Molecular and Cell Biology, i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135, Porto, Portugal.
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Barnsby-Greer L, Mabbitt PD, Dery MA, Squair DR, Wood NT, Lamoliatte F, Lange SM, Virdee S. UBE2A and UBE2B are recruited by an atypical E3 ligase module in UBR4. Nat Struct Mol Biol 2024; 31:351-363. [PMID: 38182926 PMCID: PMC10873205 DOI: 10.1038/s41594-023-01192-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 11/27/2023] [Indexed: 01/07/2024]
Abstract
UBR4 is a 574 kDa E3 ligase (E3) of the N-degron pathway with roles in neurodevelopment, age-associated muscular atrophy and cancer. The catalytic module that carries out ubiquitin (Ub) transfer remains unknown. Here we identify and characterize a distinct E3 module within human UBR4 consisting of a 'hemiRING' zinc finger, a helical-rich UBR zinc-finger interacting (UZI) subdomain, and an N-terminal region that can serve as an affinity factor for the E2 conjugating enzyme (E2). The structure of an E2-E3 complex provides atomic-level insight into the specificity determinants of the hemiRING toward the cognate E2s UBE2A/UBE2B. Via an allosteric mechanism, the UZI subdomain modestly activates the Ub-loaded E2 (E2∼Ub). We propose attenuated activation is complemented by the intrinsically high lysine reactivity of UBE2A, and their cooperation imparts a reactivity profile important for substrate specificity and optimal degradation kinetics. These findings reveal the mechanistic underpinnings of a neuronal N-degron E3, its specific recruitment of UBE2A, and highlight the underappreciated architectural diversity of cross-brace domains with Ub E3 activity.
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Affiliation(s)
- Lucy Barnsby-Greer
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Peter D Mabbitt
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
- Scion, Rotorua, New Zealand
| | - Marc-Andre Dery
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Daniel R Squair
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Nicola T Wood
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Frederic Lamoliatte
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Sven M Lange
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
| | - Satpal Virdee
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK.
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Haakonsen DL, Heider M, Ingersoll AJ, Vodehnal K, Witus SR, Uenaka T, Wernig M, Rapé M. Stress response silencing by an E3 ligase mutated in neurodegeneration. Nature 2024; 626:874-880. [PMID: 38297121 PMCID: PMC10881396 DOI: 10.1038/s41586-023-06985-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Accepted: 12/15/2023] [Indexed: 02/02/2024]
Abstract
Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis, yet their prolonged activation induces apoptosis and disrupts organismal health1-3. How stress responses are turned off at the right time and place remains poorly understood. Here we report a ubiquitin-dependent mechanism that silences the cellular response to mitochondrial protein import stress. Crucial to this process is the silencing factor of the integrated stress response (SIFI), a large E3 ligase complex mutated in ataxia and in early-onset dementia that degrades both unimported mitochondrial precursors and stress response components. By recognizing bifunctional substrate motifs that equally encode protein localization and stability, the SIFI complex turns off a general stress response after a specific stress event has been resolved. Pharmacological stress response silencing sustains cell survival even if stress resolution failed, which underscores the importance of signal termination and provides a roadmap for treating neurodegenerative diseases caused by mitochondrial import defects.
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Affiliation(s)
- Diane L Haakonsen
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Michael Heider
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Andrew J Ingersoll
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Kayla Vodehnal
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Samuel R Witus
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Takeshi Uenaka
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Marius Wernig
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Michael Rapé
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA.
- California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.
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Lyu H, Boßelmann CM, Johannesen KM, Koko M, Ortigoza-Escobar JD, Aguilera-Albesa S, Garcia-Navas Núñez D, Linnankivi T, Gaily E, van Ruiten HJA, Richardson R, Betzler C, Horvath G, Brilstra E, Geerdink N, Orsucci D, Tessa A, Gardella E, Fleszar Z, Schöls L, Lerche H, Møller RS, Liu Y. Clinical and electrophysiological features of SCN8A variants causing episodic or chronic ataxia. EBioMedicine 2023; 98:104855. [PMID: 38251463 PMCID: PMC10628346 DOI: 10.1016/j.ebiom.2023.104855] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 10/10/2023] [Accepted: 10/13/2023] [Indexed: 11/29/2023] Open
Abstract
BACKGROUND Variants in SCN8A are associated with a spectrum of epilepsies and neurodevelopmental disorders. Ataxia as a predominant symptom of SCN8A variation has not been well studied. We set out to investigate disease mechanisms and genotype-phenotype correlations of SCN8A-related ataxia. METHODS We collected genetic and electro-clinical data of ten individuals from nine unrelated families carrying novel SCN8A variants associated with chronic progressive or episodic ataxia. Electrophysiological characterizations of these variants were performed in ND7/23 cells and cultured neurons. FINDINGS Variants associated with chronic progressive ataxia either decreased Na+ current densities and shifted activation curves towards more depolarized potentials (p.Asn995Asp, p.Lys1498Glu and p.Trp1266Cys) or resulted in a premature stop codon (p.Trp937Ter). Three variants (p.Arg847Gln and biallelic p.Arg191Trp/p.Asp1525Tyr) were associated with episodic ataxia causing loss-of-function by decreasing Na+ current densities or a hyperpolarizing shift of the inactivation curve. Two additional episodic ataxia-associated variants caused mixed gain- and loss-of function effects in ND7/23 cells and were further examined in primary murine hippocampal neuronal cultures. Neuronal firing in excitatory neurons was increased by p.Arg1629His, but decreased by p.Glu1201Lys. Neuronal firing in inhibitory neurons was decreased for both variants. No functional effect was observed for p.Arg1913Trp. In four individuals, treatment with sodium channel blockers exacerbated symptoms. INTERPRETATION We identified episodic or chronic ataxia as predominant phenotypes caused by variants in SCN8A. Genotype-phenotype correlations revealed a more pronounced loss-of-function effect for variants causing chronic ataxia. Sodium channel blockers should be avoided under these conditions. FUNDING BMBF, DFG, the Italian Ministry of Health, University of Tuebingen.
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Affiliation(s)
- Hang Lyu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Christian M Boßelmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Katrine M Johannesen
- Department of Clinical Genetics, University Hospital of Copenhagen, Rigshospitalet, Copenhagen, Denmark; Department of Epilepsy Genetics and Personalized Medicine, The Danish Epilepsy Centre (Member of the ERN EpiCARE), Dianalund, Denmark
| | - Mahmoud Koko
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Juan Dario Ortigoza-Escobar
- Movement Disorders Unit, Institut de Recerca Sant Joan de Déu, CIBERER-ISCIII and European Reference Network for Rare Neurological Diseases (ERN-RND), Barcelona, Spain
| | - Sergio Aguilera-Albesa
- Pediatric Neurology Unit, Department of Pediatrics, Hospital Universitario de Navarra, Pamplona, Spain; Navarrabiomed-Fundación Miguel Servet, Pamplona, Spain
| | | | - Tarja Linnankivi
- Department of Pediatric Neurology, New Children's Hospital and Pediatric Research Center, Epilepsia Helsinki, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
| | - Eija Gaily
- Department of Pediatric Neurology, New Children's Hospital and Pediatric Research Center, Epilepsia Helsinki, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
| | - Henriette J A van Ruiten
- Newcastle Upon Tyne Hospitals NHS Foundation Trust, Great North Children's Hospital, Newcastle upon Tyne, UK
| | - Ruth Richardson
- Northern Genetics Service, The Newcastle Upon Tyne Hospitals NHS Foundation Trust, UK
| | - Cornelia Betzler
- Institute for Rehabilitation, Transition and Palliation, Paracelsus Medical University, Salzburg, Austria; Specialist Center for Paediatric Neurology, Neuro-Rehabilitation and Epileptology, Schön Klinik Vogtareuth, Germany
| | - Gabriella Horvath
- Adult Metabolic Diseases Clinic, BC Children's Hospital, Vancouver, Canada
| | - Eva Brilstra
- Department of Genetics, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Niels Geerdink
- Department of Pediatrics, Rijnstate Hospital, Arnhem, the Netherlands
| | | | | | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Medicine, The Danish Epilepsy Centre (Member of the ERN EpiCARE), Dianalund, Denmark; Department of Regional Health Research, Faculty of Health Sciences, University of Southern Denmark, Denmark
| | - Zofia Fleszar
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany; German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Ludger Schöls
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany; German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, The Danish Epilepsy Centre (Member of the ERN EpiCARE), Dianalund, Denmark; Department of Regional Health Research, Faculty of Health Sciences, University of Southern Denmark, Denmark
| | - Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany.
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Tenorio RB, Camargo CHF, Donis KC, Almeida CCB, Teive HAG. Diagnostic Yield of NGS Tests for Hereditary Ataxia: a Systematic Review. CEREBELLUM (LONDON, ENGLAND) 2023:10.1007/s12311-023-01629-y. [PMID: 37950147 DOI: 10.1007/s12311-023-01629-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/30/2023] [Indexed: 11/12/2023]
Abstract
Next-generation sequencing (NGS), comprising targeted panels (TP), exome sequencing (ES), and genome sequencing (GS) became robust clinical tools for diagnosing hereditary ataxia (HA). Determining their diagnostic yield (DY) is crucial for optimal clinical decision-making. We conducted a comprehensive systematic literature review on the DY of NGS tests for HA. We searched PubMed and Embase databases for relevant studies between 2016 and 2022 and manually examined reference lists of relevant reviews. Eligible studies described the DY of NGS tests in patients with ataxia as a significant feature. Data from 33 eligible studies showed a median DY of 43% (IQR = 9.5-100%). The median DY for TP and ES was 46% and 41.9%, respectively. Higher DY was associated with specific phenotype selection, such as episodic ataxia at 68.35% and early and late onset of ataxia at 46.4% and 54.4%. Parental consanguinity had a DY of 52.4% (p = 0.009), and the presumed autosomal recessive (AR) inheritance pattern showed 62.5%. There was a difference between the median DY of studies that performed targeted sequencing (tandem repeat expansion, TRE) screening and those that did not (p = 0.047). A weak inverse correlation was found between DY and the extent of previous genetic investigation (rho = - 0.323; p = 0.065). The most common genes were CACNA1A and SACS. DY was higher for presumed AR inheritance pattern, positive family history, and parental consanguinity. ES appears more advantageous due to the inclusion of rare genes that might be excluded in TP.
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Affiliation(s)
- Renata Barreto Tenorio
- Postgraduate Program in Internal Medicine, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, Paraná, Brazil.
| | - Carlos Henrique F Camargo
- Postgraduate Program in Internal Medicine, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, Paraná, Brazil
- Movement Disorders Sector, Neurology Service, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, Paraná, Brazil
| | - Karina Carvalho Donis
- Medical Genetics Service, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | | | - Hélio A G Teive
- Postgraduate Program in Internal Medicine, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, Paraná, Brazil
- Movement Disorders Sector, Neurology Service, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, Paraná, Brazil
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Gaudio A, Gotta F, Ponti C, Sanguineri F, Trevisan L, Geroldi A, Patrone S, Gemelli C, Cabona C, Astrea G, Fiorillo C, Gustincich S, Grandis M, Mandich P. Case report: Episodic ataxia without ataxia? Front Neurol 2023; 14:1224241. [PMID: 37965175 PMCID: PMC10640972 DOI: 10.3389/fneur.2023.1224241] [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: 05/17/2023] [Accepted: 10/03/2023] [Indexed: 11/16/2023] Open
Abstract
Hereditary myopathies represent a clinically and genetically heterogeneous group of neuromuscular disorders, characterized by highly variable clinical presentations and frequently overlapping phenotypes with other neuromuscular disorders, likely influenced by genetic and environmental modifiers. Genetic testing is often challenging due to ambiguous clinical diagnosis. Here, we present the case of a family with clinical and Electromyography (EMG) features resembling a myotonia-like disorder in which Whole Exome Sequencing (WES) analysis revealed the co-segregation of two rare missense variants in UBR4 and HSPG2, genes previously associated with episodic ataxia 8 (EA8). A review of the literature highlighted a striking overlap between the clinical and the molecular features of our family and the previously described episodic ataxias (EAs), which raises concerns about the genotype-phenotype correlation, clinical variability, and the confounding overlap in these groups of disorders. This emphasizes the importance of thoroughly framing the patient's phenotype. The more clear-cut the diagnosis, the easier the identification of a genetic determinant, and the better the prognosis and the treatment of patients.
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Affiliation(s)
- Andrea Gaudio
- IRCCS Ospedale Policlinico San Martino—UOC Genetica Medica, Genova, Italy
| | - Fabio Gotta
- IRCCS Ospedale Policlinico San Martino—UOC Genetica Medica, Genova, Italy
| | - Clarissa Ponti
- IRCCS Ospedale Policlinico San Martino—UOC Genetica Medica, Genova, Italy
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
| | - Francesca Sanguineri
- IRCCS Ospedale Policlinico San Martino—UOC Genetica Medica, Genova, Italy
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
| | - Lucia Trevisan
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
- IRCCS Ospedale Policlinico San Martino—SS Centro Tumori Ereditari, Genova, Italy
| | - Alessandro Geroldi
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
| | - Serena Patrone
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
| | - Chiara Gemelli
- IRCCS-Ospedale Policlinico San Martino—UOC Clinica Neurologica, Genova, Italy
| | - Corrado Cabona
- IRCCS-Ospedale Policlinico San Martino—UOC Neurofisiopatologia, Genova, Italy
| | | | - Chiara Fiorillo
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
- IRCCS Istituto Giannina Gaslini—UOC Neuropsichiatria Infantile, Genova, Italy
| | - Stefano Gustincich
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genova, Italy
| | - Marina Grandis
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
- IRCCS-Ospedale Policlinico San Martino—UOC Clinica Neurologica, Genova, Italy
| | - Paola Mandich
- IRCCS Ospedale Policlinico San Martino—UOC Genetica Medica, Genova, Italy
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics and Maternal and Child Health, University of Genova, Genova, Italy
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8
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Suslova M, Kortzak D, Machtens JP, Kovermann P, Fahlke C. Apo state pore opening as functional basis of increased EAAT anion channel activity in episodic ataxia 6. Front Physiol 2023; 14:1147216. [PMID: 37538371 PMCID: PMC10394623 DOI: 10.3389/fphys.2023.1147216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 07/07/2023] [Indexed: 08/05/2023] Open
Abstract
SLC1A2 and SLC1A3 encode the glial glutamate transporters EAAT2 and EAAT1, which are not only the predominant glutamate uptake carriers in our brain, but also function as anion channels. Two homologous mutations, which predict substitutions of prolines in the center of the fifth transmembrane helix by arginine (P289R EAAT2, P290R EAAT1), have been identified in patients with epileptic encephalopathy (SLC1A2) or with episodic ataxia type 6 (SLC1A3). Both mutations have been shown to impair glutamate uptake and to increase anion conduction. The molecular processes that link the disease-causing mutations to two major alterations of glutamate transporter function remain insufficiently understood. The mutated proline is conserved in every EAAT. Since the pathogenic changes mainly affect the anion channel function, we here study the functional consequences of the homologous P312R mutation in the neuronal glutamate transporter EAAT4, a low capacity glutamate transporter with predominant anion channel function. To assess the impact of charge and structure of the inserted amino acid for the observed functional changes, we generated and functionally evaluated not only P312R, but also substitutions of P312 with all other amino acids. However, only exchange of proline by arginine, lysine, histidine and asparagine were functionally tolerated. We compared WT, P312R and P312N EAAT4 using a combination of cellular electrophysiology, fast substrate application and kinetic modelling. We found that WT and mutant EAAT4 anion currents can be described with a 11-state model of the transport cycle, in which several states are connected to branching anion channel states to account for the EAAT anion channel function. Substitutions of P312 modify various transitions describing substrate binding/unbinding, translocation or anion channel opening. Most importantly, P312R generates a new anion conducting state that is accessible in the outward facing apo state and that is the main determinant of the increased anion conduction of EAAT transporters carrying this mutation. Our work provides a quantitative description how a naturally occurring mutation changes glutamate uptake and anion currents in two genetic diseases.
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Hassan A. Episodic Ataxias: Primary and Secondary Etiologies, Treatment, and Classification Approaches. Tremor Other Hyperkinet Mov (N Y) 2023; 13:9. [PMID: 37008993 PMCID: PMC10064912 DOI: 10.5334/tohm.747] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
Background Episodic ataxia (EA), characterized by recurrent attacks of cerebellar dysfunction, is the manifestation of a group of rare autosomal dominant inherited disorders. EA1 and EA2 are most frequently encountered, caused by mutations in KCNA1 and CACNA1A. EA3-8 are reported in rare families. Advances in genetic testing have broadened the KCNA1 and CACNA1A phenotypes, and detected EA as an unusual presentation of several other genetic disorders. Additionally, there are various secondary causes of EA and mimicking disorders. Together, these can pose diagnostic challenges for neurologists. Methods A systematic literature review was performed in October 2022 for 'episodic ataxia' and 'paroxysmal ataxia', restricted to publications in the last 10 years to focus on recent clinical advances. Clinical, genetic, and treatment characteristics were summarized. Results EA1 and EA2 phenotypes have further broadened. In particular, EA2 may be accompanied by other paroxysmal disorders of childhood with chronic neuropsychiatric features. New treatments for EA2 include dalfampridine and fampridine, in addition to 4-aminopyridine and acetazolamide. There are recent proposals for EA9-10. EA may also be caused by gene mutations associated with chronic ataxias (SCA-14, SCA-27, SCA-42, AOA2, CAPOS), epilepsy syndromes (KCNA2, SCN2A, PRRT2), GLUT-1, mitochondrial disorders (PDHA1, PDHX, ACO2), metabolic disorders (Maple syrup urine disease, Hartnup disease, type I citrullinemia, thiamine and biotin metabolism defects), and others. Secondary causes of EA are more commonly encountered than primary EA (vascular, inflammatory, toxic-metabolic). EA can be misdiagnosed as migraine, peripheral vestibular disorders, anxiety, and functional symptoms. Primary and secondary EA are frequently treatable which should prompt a search for the cause. Discussion EA may be overlooked or misdiagnosed for a variety of reasons, including phenotype-genotype variability and clinical overlap between primary and secondary causes. EA is highly treatable, so it is important to consider in the differential diagnosis of paroxysmal disorders. Classical EA1 and EA2 phenotypes prompt single gene test and treatment pathways. For atypical phenotypes, next generation genetic testing can aid diagnosis and guide treatment. Updated classification systems for EA are discussed which may assist diagnosis and management.
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10
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Erro R, Magrinelli F, Bhatia KP. Paroxysmal movement disorders: Paroxysmal dyskinesia and episodic ataxia. HANDBOOK OF CLINICAL NEUROLOGY 2023; 196:347-365. [PMID: 37620078 DOI: 10.1016/b978-0-323-98817-9.00033-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Paroxysmal movement disorders have traditionally been classified into paroxysmal dyskinesia (PxD), which consists in attacks of involuntary movements (mainly dystonia and/or chorea) without loss of consciousness, and episodic ataxia (EA), which features spells of cerebellar dysfunction with or without interictal neurological manifestations. In this chapter, PxD will be discussed first according to the trigger-based classification, thus reviewing clinical, genetic, and molecular features of paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exercise-induced dyskinesia. EA will be presented thereafter according to their designated gene or genetic locus. Clinicogenetic similarities among paroxysmal movement disorders have progressively emerged, which are herein highlighted along with growing evidence that their pathomechanisms overlap those of epilepsy and migraine. Advances in our comprehension of the biological pathways underlying paroxysmal movement disorders, which involve ion channels as well as proteins associated with the vesical synaptic cycle or implicated in neuronal energy metabolism, may represent the cornerstone for defining a shared pathophysiologic framework and developing target-specific therapies.
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Affiliation(s)
- Roberto Erro
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", Neuroscience Section, University of Salerno, Baronissi, Salerno, Italy
| | - Francesca Magrinelli
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Kailash P Bhatia
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
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11
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Chen I, Wu Q, Font J, Ryan RM. The twisting elevator mechanism of glutamate transporters reveals the structural basis for the dual transport-channel functions. Curr Opin Struct Biol 2022; 75:102405. [PMID: 35709614 DOI: 10.1016/j.sbi.2022.102405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/10/2022] [Accepted: 05/12/2022] [Indexed: 11/16/2022]
Abstract
Glutamate transporters facilitate the removal of this excitatory neurotransmitter from the synapse. Increasing evidence indicates that this process is linked to intrinsic chloride channel activity that is thermodynamically uncoupled from substrate transport. A recent cryo-EM structure of GltPh - an archaeal homolog of the glutamate transporters - in an open channel state has shed light on the structural basis for channel opening formed at the interface of two domains within the transporter which is gated by two clusters of hydrophobic residues. These transporters cycle through several conformational states during the transport process, including the chloride conducting state, which appears to be stabilised by protein-membrane interactions and membrane deformation. Several point mutations that perturb the chloride conductance can have detrimental effects and are linked to the pathogenesis of the neurological disorder, episodic ataxia type 6.
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Affiliation(s)
- Ichia Chen
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Qianyi Wu
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Josep Font
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia.
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12
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Ghorbani F, Alimohamed MZ, Vilacha JF, Van Dijk KK, De Boer-Bergsma J, Fokkens MR, Lemmink H, Sijmons RH, Sikkema-Raddatz B, Groves MR, Verschuuren-Bemelmans CC, Verbeek DS, Van Diemen CC, Westers H. Feasibility of Follow-Up Studies and Reclassification in Spinocerebellar Ataxia Gene Variants of Unknown Significance. Front Genet 2022; 13:782685. [PMID: 35401678 PMCID: PMC8990126 DOI: 10.3389/fgene.2022.782685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative disorders with autosomal dominant inheritance. Genetic testing for SCA leads to diagnosis, prognosis and risk assessment for patients and their family members. While advances in sequencing and computing technologies have provided researchers with a rapid expansion in the genetic test content that can be used to unravel the genetic causes that underlie diseases, the large number of variants with unknown significance (VUSes) detected represent challenges. To minimize the proportion of VUSes, follow-up studies are needed to aid in their reclassification as either (likely) pathogenic or (likely) benign variants. In this study, we addressed the challenge of prioritizing VUSes for follow-up using (a combination of) variant segregation studies, 3D protein modeling, in vitro splicing assays and functional assays. Of the 39 VUSes prioritized for further analysis, 13 were eligible for follow up. We were able to reclassify 4 of these VUSes to LP, increasing the molecular diagnostic yield by 1.1%. Reclassification of VUSes remains difficult due to limited possibilities for performing variant segregation studies in the classification process and the limited availability of routine functional tests.
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Affiliation(s)
- Fatemeh Ghorbani
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Mohamed Z. Alimohamed
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
- Department of Hematology and Blood Transfusion, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
- Shree Hindu Mandal Hospital, Dar es Salaam, Tanzania
| | - Juliana F. Vilacha
- Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, Groningen, Netherlands
| | - Krista K. Van Dijk
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Jelkje De Boer-Bergsma
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Michiel R. Fokkens
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Henny Lemmink
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Rolf H. Sijmons
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Birgit Sikkema-Raddatz
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Matthew R. Groves
- Structural Biology in Drug Design, Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
| | | | - Dineke S. Verbeek
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
- *Correspondence: Dineke S. Verbeek,
| | - Cleo C. Van Diemen
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Helga Westers
- Department of Genetics, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
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13
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UBR4/POE facilitates secretory trafficking to maintain circadian clock synchrony. Nat Commun 2022; 13:1594. [PMID: 35332162 PMCID: PMC8948264 DOI: 10.1038/s41467-022-29244-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 03/02/2022] [Indexed: 11/08/2022] Open
Abstract
Ubiquitin ligases control the degradation of core clock proteins to govern the speed and resetting properties of the circadian pacemaker. However, few studies have addressed their potential to regulate other cellular events within clock neurons beyond clock protein turnover. Here, we report that the ubiquitin ligase, UBR4/POE, strengthens the central pacemaker by facilitating neuropeptide trafficking in clock neurons and promoting network synchrony. Ubr4-deficient mice are resistant to jetlag, whereas poe knockdown flies are prone to arrhythmicity, behaviors reflective of the reduced axonal trafficking of circadian neuropeptides. At the cellular level, Ubr4 ablation impairs the export of secreted proteins from the Golgi apparatus by reducing the expression of Coronin 7, which is required for budding of Golgi-derived transport vesicles. In summary, UBR4/POE fulfills a conserved and unexpected role in the vesicular trafficking of neuropeptides, a function that has important implications for circadian clock synchrony and circuit-level signal processing. Although ubiquitin ligases are known to control clock protein degradation, their other roles in clock neurons are unclear. Here the authors report that UBR4 promotes export of neuropeptides from the Golgi for axonal trafficking, which is important for circadian clock synchrony in mice and flies.
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14
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Wu Q, Akhter A, Pant S, Cho E, Zhu JX, Garner AR, Ohyama T, Tajkhorshid E, van Meyel DJ, Ryan RM. Ataxia-linked SLC1A3 mutations alter EAAT1 chloride channel activity and glial regulation of CNS function. J Clin Invest 2022; 132:154891. [PMID: 35167492 PMCID: PMC8970671 DOI: 10.1172/jci154891] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/08/2022] [Indexed: 11/17/2022] Open
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). Excitatory Amino Acid Transporters (EAATs) regulate extracellular glutamate by transporting it into cells, mostly glia, to terminate neurotransmission and to avoid neurotoxicity. EAATs are also chloride (Cl-) channels, but the physiological role of Cl- conductance through EAATs is poorly understood. Mutations of human EAAT1 (hEAAT1) have been identified in patients with episodic ataxia type 6 (EA6). One mutation showed increased Cl- channel activity and decreased glutamate transport, but the relative contributions of each function of hEAAT1 to mechanisms underlying the pathology of EA6 remain unclear. Here we investigated the effects of five additional EA6-related mutations on hEAAT1 function in Xenopus laevis oocytes, and on CNS function in a Drosophila melanogaster model of locomotor behavior. Our results indicate that mutations resulting in decreased hEAAT1 Cl- channel activity but with functional glutamate transport can also contribute to the pathology of EA6, highlighting the importance of Cl- homeostasis in glial cells for proper CNS function. We also identified a novel mechanism involving an ectopic sodium (Na+) leak conductance in glial cells. Together, these results strongly support the idea that EA6 is primarily an ion channelopathy of CNS glia.
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Affiliation(s)
- Qianyi Wu
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Azman Akhter
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Shashank Pant
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Eunjoo Cho
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Jin Xin Zhu
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | | | - Tomoko Ohyama
- Department of Biology, McGill University, Montreal, Canada
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Donald J van Meyel
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Renae M Ryan
- School of Medical Sciences, University of Sydney, Sydney, Australia
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15
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Kovermann P, Engels M, Müller F, Fahlke C. Cellular Physiology and Pathophysiology of EAAT Anion Channels. Front Cell Neurosci 2022; 15:815279. [PMID: 35087380 PMCID: PMC8787812 DOI: 10.3389/fncel.2021.815279] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/13/2021] [Indexed: 11/17/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) optimize the temporal resolution and energy demand of mammalian excitatory synapses by quickly removing glutamate from the synaptic cleft into surrounding neuronal and glial cells and ensuring low resting glutamate concentrations. In addition to secondary active glutamate transport, EAATs also function as anion channels. The channel function of these transporters is conserved in all homologs ranging from archaebacteria to mammals; however, its physiological roles are insufficiently understood. There are five human EAATs, which differ in their glutamate transport rates. Until recently the high-capacity transporters EAAT1, EAAT2, and EAAT3 were believed to conduct only negligible anion currents, with no obvious function in cell physiology. In contrast, the low-capacity glutamate transporters EAAT4 and EAAT5 are thought to regulate neuronal signaling as glutamate-gated channels. In recent years, new experimental approaches and novel animal models, together with the discovery of a human genetic disease caused by gain-of-function mutations in EAAT anion channels have enabled identification of the first physiological and pathophysiological roles of EAAT anion channels.
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16
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Sharawat IK, Panda PK, Bhunia NS, Dawman L. Clinical Spectrum of TGM6-Related Movement Disorders: A New Report with a Pooled Analysis of 48 Patients. J Neurosci Rural Pract 2021; 12:656-665. [PMID: 34737499 PMCID: PMC8559089 DOI: 10.1055/s-0041-1734006] [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] [Indexed: 11/13/2022] Open
Abstract
Background
Spinocerebellar ataxias (SCAs) are a diverse group of progressive neurodegenerative disorders. Until now, more than 20 genes have been implicated to be associated with this phenotype and
TGM6
is one of these genes, associated with spinocerebellar ataxia-35 (SCA-35). The majority of disease-causing variants in the
TGM6
gene predominantly have been reported from China and Taiwan and the association with Parkinson's disease (PD) have also been reported recently.
Methods
We report the first Indian case with SCA-35 in a 16-year-old-boy with atypical age of onset at 9 years, prominent extrapyramidal features, intellectual disability, and a novel missense mutation in the
TGM6
gene. We also reviewed and collated all previously published cases with pathogenic TGM6 variants.
Results
Including the index case, 54 cases were identified from 10 relevant articles in literature and 48 cases had adequate clinical details to be included in the pooled analysis. Around two-thirds of reported cases had SCA-35 phenotype, with cerebellar atrophy. Onset in the majority of cases was the fourth decade of life onwards. A proportion of SCA-35 cases also had spasmodic torticollis, impaired proprioception, extrapyramidal features, and myoclonic jerks. The patients with PD had often early-onset milder symptoms, slower progression, and favorable response to levodopa/carbidopa. One patient each presented with episodic ataxia and dystonic tremor of the upper limb. Most of the cases had missense mutations, without any definite hotspot or genotype–phenotype correlation.
Conclusions
TGM6 mutation should be suspected in patients with SCA like presentation, especially when it is accompanied by extrapyramidal features, spasmodic torticollis, impaired proprioception, or myoclonus.
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Affiliation(s)
- Indar Kumar Sharawat
- Department of Pediatrics, Pediatric Neurology Division, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Prateek Kumar Panda
- Department of Pediatrics, Pediatric Neurology Division, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Niladri Sekhar Bhunia
- Department of Pediatrics, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Lesa Dawman
- Department of Pediatrics, Post Graduate Institute of Medical Education and Research, Chandigarh, India
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17
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Alehabib E, Esmaeilizadeh Z, Ranji-Burachaloo S, Tafakhori A, Darvish H, Movafagh A. Clinical and molecular spectrum of P/Q type calcium channel Cav2.1 in epileptic patients. Orphanet J Rare Dis 2021; 16:461. [PMID: 34727962 PMCID: PMC8562004 DOI: 10.1186/s13023-021-02101-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 10/24/2021] [Indexed: 11/24/2022] Open
Abstract
Background Epilepsy is a neurological disorder characterized by the potential to induce seizure and accompanied by cognitive, psychological, and social consequences. CACNA1A gene is a voltage-gated P/Q-type Cav2.1 channel that is broadly expressed in the central nervous system, and the pathogenic variants within this gene may be associated with the epileptic phenotype. In the present study, we collected clinical and molecular data related to epileptic patients with CACNA1A pathogenic variants and investigated possible meaningful relationship between age at onset, neurodevelopmental disorders, type of seizures, brain imaging abnormalities, genotype, and protein domains. Results In our retrospective literature studies, from among 890 articles reviewed, a total of 90 individuals were related to epilepsy phenotype. Our findings showed that about 90 percent of patients have shown the first symptoms in childhood and teenage years and different types of neurodevelopmental disorders, such as intellectual disability, developmental arrest, and behavioral disorders, have been common findings for these patients. Further, a wide range of abnormalities have been observed in their brain imaging, and generalized seizures have been the most type of seizures in these patients. However, our data showed no specific genotype–phenotype correlation in epileptic patients with CACNA1A pathogenic alterations. Conclusions Our study focused on epileptic phenotype in patients with CACNA1A pathogenic variants and showed a wide range of clinical and molecular heterogeneity with no specific genotype–phenotype correlation. It seems that incomplete penetrance, de-novo variants, and modifier genes are obstacles in predicting the clinical outcome. Supplementary Information The online version contains supplementary material available at 10.1186/s13023-021-02101-y.
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Affiliation(s)
- Elham Alehabib
- Student Research Committee, Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Zahra Esmaeilizadeh
- Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sakineh Ranji-Burachaloo
- Iranian Center of Neurological Research, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Abbas Tafakhori
- Iranian Center of Neurological Research, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Hossein Darvish
- Neuroscience Research Center, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran
| | - Abolfazl Movafagh
- Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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18
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Choi JH, Oh EH, Choi SY, Kim HJ, Lee SK, Choi JY, Kim JS, Choi KD. Vestibular impairments in episodic ataxia type 2. J Neurol 2021; 269:2687-2695. [PMID: 34709445 DOI: 10.1007/s00415-021-10856-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 10/20/2022]
Abstract
Episodic ataxia type 2 (EA2) can present diverse ocular motor abnormalities, but few studies have systematically evaluated vestibular function during the interictal periods. This study aimed to determine vestibular impairments in patients with EA2 during the interictal periods. We recruited 17 patients with genetically confirmed EA2 (10 men, age range = 16-85 years, median = 32 years). We systematically evaluated the vestibular function by measuring the semicircular canals (SCCs) function with bithermal caloric tests, rotatory chair test, and video head impulse test (vHIT), and the otolith function with subjective visual vertical (SVV) tilt and variability, and cervical and ocular vestibular-evoked myogenic potentials (VEMPs). Patients with EA2 commonly showed abnormal VOR responses at least for one SCC with high-acceleration, high-frequency head impulses (14/16, 88%), and impaired visual-vestibular interaction (7/12, 58%). In response to low acceleration and frequency stimuli, the VOR gains were generally normal. The majority of EA2 patients had impairments in at least one of the otolith function tests (13/16, 81%): SVV tilt or variability (7/14, 50%), oVEMP (8/15, 53%), and cVEMP (4/16, 25%). Vestibular impairments are common in EA2 even during the interictal periods. Selective decrease in the VOR responses during higher acceleration stimuli along with impaired visual-vestibular interaction and otolith function suggests degeneration of the vestibulocerebellum or vestibular nuclei.
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Affiliation(s)
- Jae-Hwan Choi
- Department of Neurology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, South Korea
| | - Eun Hye Oh
- Department of Neurology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, South Korea
| | - Seo Young Choi
- Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine and Biomedical Research Institute, Busan, South Korea
| | - Hyo Jung Kim
- Research Administration Team, Seoul National University Bundang Hospital, Seongnam, South Korea
| | - Seon Kyung Lee
- Dizziness Center, Clinical Neuroscience Center, Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, Gyeonggi-do, 13620, South Korea
| | - Jeong Yoon Choi
- Dizziness Center, Clinical Neuroscience Center, Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, Gyeonggi-do, 13620, South Korea
| | - Ji-Soo Kim
- Dizziness Center, Clinical Neuroscience Center, Department of Neurology, Seoul National University Bundang Hospital, 173-82 Gumi-ro, Bundang-gu, Seongnam, Gyeonggi-do, 13620, South Korea.
| | - Kwang-Dong Choi
- Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine and Biomedical Research Institute, Busan, South Korea. .,Department of Neurology, College of Medicine, Pusan National University Hospital, 1-10 Ami-dong, Seo-gu, Busan, 49241, South Korea.
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Kubota T, Nabatame S, Sato R, Hama M, Nishiike U, Mochizuki H, Takahashi MP, Takeshima T. Hemiplegic migraine type 2 caused by a novel variant within the P-type ATPase motif in ATP1A2 concomitant with a CACNA1A variant. Brain Dev 2021; 43:952-957. [PMID: 34092402 DOI: 10.1016/j.braindev.2021.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 05/15/2021] [Accepted: 05/18/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Familial hemiplegic migraine (FHM) is an inherited autosomal dominant disorder characterized by migraine with reversible hemiplegia. FHM1 is caused by variants in CACNA1A, encoding a P/Q type neuronal voltage-gated calcium channel α subunit, which is also associated with episodic ataxia type 2 (EA2). FHM2 is associated with ATP1A2, which codes for an Na+/K+-ATPase isoform 2 subunit. CASE PRESENTATION We identified an FHM2 family, the mother and her daughter, with a novel variant in ATP1A2, p.Gly377Asp, located in a well-conserved P-type ATPase motif. Additionally, the mother harbored deletion in the CACNA1A, associated with EA2, but her daughter did not. The mother presented migraine with typical aura without motor deficit, whereas her daughter had migraine accompanied by recurrent motor deficit and altered consciousness. The additional CACNA1A deletion in the mother might serve as a modifier. CONCLUSION Our report emphasizes the importance of genetic analysis to diagnose neurological ion channel/transporter diseases.
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Affiliation(s)
- Tomoya Kubota
- Department of Clinical Laboratory and Biomedical Sciences, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7, Yamadaoka, Suita, Osaka 5650871, Japan; Department of Neurology, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Shin Nabatame
- Department of Pediatrics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Ruka Sato
- Department of Clinical Laboratory and Biomedical Sciences, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Manami Hama
- Department of Clinical Laboratory and Biomedical Sciences, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Ujiakira Nishiike
- Department of Neurology, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Hideki Mochizuki
- Department of Neurology, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Masanori P Takahashi
- Department of Clinical Laboratory and Biomedical Sciences, Division of Health Sciences, Osaka University Graduate School of Medicine, 1-7, Yamadaoka, Suita, Osaka 5650871, Japan; Department of Neurology, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka 5650871, Japan.
| | - Takao Takeshima
- Department of Neurology, Tominaga Hospital, 1-4-48, Minato-cho, Naniwa-ku, Osaka, Osaka 5560017, Japan.
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20
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Lauxmann S, Sonnenberg L, Koch NA, Bosselmann C, Winter N, Schwarz N, Wuttke TV, Hedrich UBS, Liu Y, Lerche H, Benda J, Kegele J. Therapeutic Potential of Sodium Channel Blockers as a Targeted Therapy Approach in KCNA1-Associated Episodic Ataxia and a Comprehensive Review of the Literature. Front Neurol 2021; 12:703970. [PMID: 34566847 PMCID: PMC8459024 DOI: 10.3389/fneur.2021.703970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 07/23/2021] [Indexed: 11/17/2022] Open
Abstract
Introduction: Among genetic paroxysmal movement disorders, variants in ion channel coding genes constitute a major subgroup. Loss-of-function (LOF) variants in KCNA1, the gene coding for KV1.1 channels, are associated with episodic ataxia type 1 (EA1), characterized by seconds to minutes-lasting attacks including gait incoordination, limb ataxia, truncal instability, dysarthria, nystagmus, tremor, and occasionally seizures, but also persistent neuromuscular symptoms like myokymia or neuromyotonia. Standard treatment has not yet been developed, and different treatment efforts need to be systematically evaluated. Objective and Methods: Personalized therapeutic regimens tailored to disease-causing pathophysiological mechanisms may offer the specificity required to overcome limitations in therapy. Toward this aim, we (i) reviewed all available clinical reports on treatment response and functional consequences of KCNA1 variants causing EA1, (ii) examined the potential effects on neuronal excitability of all variants using a single compartment conductance-based model and set out to assess the potential of two sodium channel blockers (SCBs: carbamazepine and riluzole) to restore the identified underlying pathophysiological effects of KV1.1 channels, and (iii) provide a comprehensive review of the literature considering all types of episodic ataxia. Results: Reviewing the treatment efforts of EA1 patients revealed moderate response to acetazolamide and exhibited the strength of SCBs, especially carbamazepine, in the treatment of EA1 patients. Biophysical dysfunction of KV1.1 channels is typically based on depolarizing shifts of steady-state activation, leading to an LOF of KCNA1 variant channels. Our model predicts a lowered rheobase and an increase of the firing rate on a neuronal level. The estimated concentration dependent effects of carbamazepine and riluzole could partially restore the altered gating properties of dysfunctional variant channels. Conclusion: These data strengthen the potential of SCBs to contribute to functional compensation of dysfunctional KV1.1 channels. We propose riluzole as a new drug repurposing candidate and highlight the role of personalized approaches to develop standard care for EA1 patients. These results could have implications for clinical practice in future and highlight the need for the development of individualized and targeted therapies for episodic ataxia and genetic paroxysmal disorders in general.
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Affiliation(s)
- Stephan Lauxmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Lukas Sonnenberg
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Nils A. Koch
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Christian Bosselmann
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Natalie Winter
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Niklas Schwarz
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Thomas V. Wuttke
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Department of Neurosurgery, University of Tübingen, Tübingen, Germany
| | - Ulrike B. S. Hedrich
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Yuanyuan Liu
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Jan Benda
- Institute of Neurobiology, University of Tübingen, Tübingen, Germany
- Bernstein Center for Computational Neuroscience Tübingen, Tübingen, Germany
| | - Josua Kegele
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
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21
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Rare Gain-of-Function KCND3 Variant Associated with Cerebellar Ataxia, Parkinsonism, Cognitive Dysfunction, and Brain Iron Accumulation. Int J Mol Sci 2021; 22:ijms22158247. [PMID: 34361012 PMCID: PMC8347726 DOI: 10.3390/ijms22158247] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 01/08/2023] Open
Abstract
Loss-of-function mutations in the KV4.3 channel-encoding KCND3 gene are linked to neurodegenerative cerebellar ataxia. Patients suffering from neurodegeneration associated with iron deposition may also present with cerebellar ataxia. The mechanism underlying brain iron accumulation remains unclear. Here, we aim to ascertain the potential pathogenic role of KCND3 variant in iron accumulation-related cerebellar ataxia. We presented a patient with slowly progressive cerebellar ataxia, parkinsonism, cognitive impairment, and iron accumulation in the basal ganglia and the cerebellum. Whole exome sequencing analyses identified in the patient a heterozygous KCND3 c.1256G>A (p.R419H) variant predicted to be disease-causing by multiple bioinformatic analyses. In vitro biochemical and immunofluorescence examinations revealed that, compared to the human KV4.3 wild-type channel, the p.R419H variant exhibited normal protein abundance and subcellular localization pattern. Electrophysiological investigation, however, demonstrated that the KV4.3 p.R419H variant was associated with a dominant increase in potassium current amplitudes, as well as notable changes in voltage-dependent gating properties leading to enhanced potassium window current. These observations indicate that, in direct contrast with the loss-of-function KCND3 mutations previously reported in cerebellar ataxia patients, we identified a rare gain-of-function KCND3 variant that may expand the clinical and molecular spectra of neurodegenerative cerebellar disorders associated with brain iron accumulation.
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22
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Harvey S, King MD, Gorman KM. Paroxysmal Movement Disorders. Front Neurol 2021; 12:659064. [PMID: 34177764 PMCID: PMC8232056 DOI: 10.3389/fneur.2021.659064] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/20/2021] [Indexed: 11/13/2022] Open
Abstract
Paroxysmal movement disorders (PxMDs) are a clinical and genetically heterogeneous group of movement disorders characterized by episodic involuntary movements (dystonia, dyskinesia, chorea and/or ataxia). Historically, PxMDs were classified clinically (triggers and characteristics of the movements) and this directed single-gene testing. With the advent of next-generation sequencing (NGS), how we classify and investigate PxMDs has been transformed. Next-generation sequencing has enabled new gene discovery (RHOBTB2, TBC1D24), expansion of phenotypes in known PxMDs genes and a better understanding of disease mechanisms. However, PxMDs exhibit phenotypic pleiotropy and genetic heterogeneity, making it challenging to predict genotype based on the clinical phenotype. For example, paroxysmal kinesigenic dyskinesia is most commonly associated with variants in PRRT2 but also variants identified in PNKD, SCN8A, and SCL2A1. There are no radiological or biochemical biomarkers to differentiate genetic causes. Even with NGS, diagnosis rates are variable, ranging from 11 to 51% depending on the cohort studied and technology employed. Thus, a large proportion of patients remain undiagnosed compared to other neurological disorders such as epilepsy, highlighting the need for further genomic research in PxMDs. Whole-genome sequencing, deep-sequencing, copy number variant analysis, detection of deep-intronic variants, mosaicism and repeat expansions, will improve diagnostic rates. Identifying the underlying genetic cause has a significant impact on patient care, modification of treatment, long-term prognostication and genetic counseling. This paper provides an update on the genetics of PxMDs, description of PxMDs classified according to causative gene rather than clinical phenotype, highlighting key clinical features and providing an algorithm for genetic testing of PxMDs.
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Affiliation(s)
- Susan Harvey
- Department of Paediatric Neurology and Clinical Neurophysiology, Children's Health Ireland at Temple Street, Dublin, Ireland
| | - Mary D King
- Department of Paediatric Neurology and Clinical Neurophysiology, Children's Health Ireland at Temple Street, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Kathleen M Gorman
- Department of Paediatric Neurology and Clinical Neurophysiology, Children's Health Ireland at Temple Street, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
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23
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Martínez-Monseny AF, Edo A, Casas-Alba D, Izquierdo-Serra M, Bolasell M, Conejo D, Martorell L, Muchart J, Carrera L, Ortez CI, Nascimento A, Oliva B, Fernández-Fernández JM, Serrano M. CACNA1A Mutations Causing Early Onset Ataxia: Profiling Clinical, Dysmorphic and Structural-Functional Findings. Int J Mol Sci 2021; 22:ijms22105180. [PMID: 34068417 PMCID: PMC8153625 DOI: 10.3390/ijms22105180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 01/07/2023] Open
Abstract
The CACNA1A gene encodes the pore-forming α1A subunit of the voltage-gated CaV2.1 Ca2+ channel, essential in neurotransmission, especially in Purkinje cells. Mutations in CACNA1A result in great clinical heterogeneity with progressive symptoms, paroxysmal events or both. During infancy, clinical and neuroimaging findings may be unspecific, and no dysmorphic features have been reported. We present the clinical, radiological and evolutionary features of three patients with congenital ataxia, one of them carrying a new variant. We report the structural localization of variants and their expected functional consequences. There was an improvement in cerebellar syndrome over time despite a cerebellar atrophy progression, inconsistent response to acetazolamide and positive response to methylphenidate. The patients shared distinctive facial gestalt: oval face, prominent forehead, hypertelorism, downslanting palpebral fissures and narrow nasal bridge. The two α1A affected residues are fully conserved throughout evolution and among the whole human CaV channel family. They contribute to the channel pore and the voltage sensor segment. According to structural data analysis and available functional characterization, they are expected to exert gain- (F1394L) and loss-of-function (R1664Q/R1669Q) effect, respectively. Among the CACNA1A-related phenotypes, our results suggest that non-progressive congenital ataxia is associated with developmental delay and dysmorphic features, constituting a recognizable syndromic neurodevelopmental disorder.
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Affiliation(s)
- Antonio F. Martínez-Monseny
- Department of Genetic and Molecular Medicine, Institut de Recerca, Hospital Sant Joan de Déu, 08950 Barcelona, Spain; (A.F.M.-M.); (D.C.-A.); (M.B.); (L.M.)
| | - Albert Edo
- Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain; (A.E.); (M.I.-S.)
| | - Dídac Casas-Alba
- Department of Genetic and Molecular Medicine, Institut de Recerca, Hospital Sant Joan de Déu, 08950 Barcelona, Spain; (A.F.M.-M.); (D.C.-A.); (M.B.); (L.M.)
| | - Mercè Izquierdo-Serra
- Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain; (A.E.); (M.I.-S.)
| | - Mercè Bolasell
- Department of Genetic and Molecular Medicine, Institut de Recerca, Hospital Sant Joan de Déu, 08950 Barcelona, Spain; (A.F.M.-M.); (D.C.-A.); (M.B.); (L.M.)
| | - David Conejo
- Pediatric Department, Complejo Asistencial de Burgos, 09006 Burgos, Spain;
| | - Loreto Martorell
- Department of Genetic and Molecular Medicine, Institut de Recerca, Hospital Sant Joan de Déu, 08950 Barcelona, Spain; (A.F.M.-M.); (D.C.-A.); (M.B.); (L.M.)
- U-703 Centre for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, 08002 Barcelona, Spain; (C.I.O.); (A.N.)
| | - Jordi Muchart
- Pediatric Radiology Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, 08950 Barcelona, Spain;
| | - Laura Carrera
- Neuropediatric Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, 08950 Barcelona, Spain;
| | - Carlos I. Ortez
- U-703 Centre for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, 08002 Barcelona, Spain; (C.I.O.); (A.N.)
- Neuropediatric Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, 08950 Barcelona, Spain;
| | - Andrés Nascimento
- U-703 Centre for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, 08002 Barcelona, Spain; (C.I.O.); (A.N.)
- Neuropediatric Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, 08950 Barcelona, Spain;
| | - Baldo Oliva
- Structural Bioinformatics Lab, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain;
| | - José M. Fernández-Fernández
- Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain; (A.E.); (M.I.-S.)
- Correspondence: (J.M.F.-F.); (M.S.); Tel.: +34-93-3160854 (J.M.F.-F.); +34-93-253-2100 (M.S.)
| | - Mercedes Serrano
- U-703 Centre for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, 08002 Barcelona, Spain; (C.I.O.); (A.N.)
- Neuropediatric Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, 08950 Barcelona, Spain;
- Correspondence: (J.M.F.-F.); (M.S.); Tel.: +34-93-3160854 (J.M.F.-F.); +34-93-253-2100 (M.S.)
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24
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Novel KCND3 Variant Underlying Nonprogressive Congenital Ataxia or SCA19/22 Disrupt K V4.3 Protein Expression and K+ Currents with Variable Effects on Channel Properties. Int J Mol Sci 2021; 22:ijms22094986. [PMID: 34067185 PMCID: PMC8125845 DOI: 10.3390/ijms22094986] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 04/28/2021] [Accepted: 05/04/2021] [Indexed: 02/07/2023] Open
Abstract
KCND3 encodes the voltage-gated potassium channel KV4.3 that is highly expressed in the cerebellum, where it regulates dendritic excitability and calcium influx. Loss-of-function KV4.3 mutations have been associated with dominant spinocerebellar ataxia (SCA19/22). By targeted NGS sequencing, we identified two novel KCND3 missense variants of the KV4.3 channel: p.S347W identified in a patient with adult-onset pure cerebellar syndrome and p.W359G detected in a child with congenital nonprogressive ataxia. Neuroimaging showed mild cerebellar atrophy in both patients. We performed a two-electrode voltage-clamp recording of KV4.3 currents in Xenopus oocytes: both the p.G345V (previously reported in a SCA19/22 family) and p.S347W mutants exhibited reduced peak currents by 50%, while no K+ current was detectable for the p.W359G mutant. We assessed the effect of the mutations on channel gating by measuring steady-state voltage-dependent activation and inactivation properties: no significant alterations were detected in p.G345V and p.S347W disease-associated variants, compared to controls. KV4.3 expression studies in HEK293T cells showed 53% (p.G345V), 45% (p.S347W) and 75% (p.W359G) reductions in mutant protein levels compared with the wildtype. The present study broadens the spectrum of the known phenotypes and identifies additional variants for KCND3-related disorders, outlining the importance of SCA gene screening in early-onset and congenital ataxia.
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25
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Bhat S, El-Kasaby A, Freissmuth M, Sucic S. Functional and Biochemical Consequences of Disease Variants in Neurotransmitter Transporters: A Special Emphasis on Folding and Trafficking Deficits. Pharmacol Ther 2020; 222:107785. [PMID: 33310157 PMCID: PMC7612411 DOI: 10.1016/j.pharmthera.2020.107785] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/02/2020] [Indexed: 01/30/2023]
Abstract
Neurotransmitters, such as γ-aminobutyric acid, glutamate, acetyl choline, glycine and the monoamines, facilitate the crosstalk within the central nervous system. The designated neurotransmitter transporters (NTTs) both release and take up neurotransmitters to and from the synaptic cleft. NTT dysfunction can lead to severe pathophysiological consequences, e.g. epilepsy, intellectual disability, or Parkinson’s disease. Genetic point mutations in NTTs have recently been associated with the onset of various neurological disorders. Some of these mutations trigger folding defects in the NTT proteins. Correct folding is a prerequisite for the export of NTTs from the endoplasmic reticulum (ER) and the subsequent trafficking to their pertinent site of action, typically at the plasma membrane. Recent studies have uncovered some of the key features in the molecular machinery responsible for transporter protein folding, e.g., the role of heat shock proteins in fine-tuning the ER quality control mechanisms in cells. The therapeutic significance of understanding these events is apparent from the rising number of reports, which directly link different pathological conditions to NTT misfolding. For instance, folding-deficient variants of the human transporters for dopamine or GABA lead to infantile parkinsonism/dystonia and epilepsy, respectively. From a therapeutic point of view, some folding-deficient NTTs are amenable to functional rescue by small molecules, known as chemical and pharmacological chaperones.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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26
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Chivukula AS, Suslova M, Kortzak D, Kovermann P, Fahlke C. Functional consequences of SLC1A3 mutations associated with episodic ataxia 6. Hum Mutat 2020; 41:1892-1905. [PMID: 32741053 DOI: 10.1002/humu.24089] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/09/2020] [Accepted: 07/27/2020] [Indexed: 11/09/2022]
Abstract
The episodic ataxias (EA) are a group of inherited neurological diseases characterized by paroxysmal cerebellar incoordination. There exist nine forms of episodic ataxia with distinct neurological symptoms and genetic origins. Episodic ataxia type 6 (EA6) differs from other EA forms in long attack duration, epilepsy and absent myokymia, nystagmus, and tinnitus. It has been described in seven families, and mutations in SLC1A3, the gene encoding the glial glutamate transporter EAAT1, were reported in each family. How these mutations affect EAAT1 expression, subcellular localization, and function, and how such alterations result in the complex neurological phenotype of EA6 is insufficiently understood. We here compare the functional consequences of all currently known mutations by heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch clamp recordings of EAAT1 transport and anion currents. We observed impairments of multiple EAAT1 properties ranging from changes in transport function, impaired trafficking to increased protein expression. Many mutations caused only slight changes illustrating how sensitively the cerebellum reacts on impaired EAAT1 functions.
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Affiliation(s)
- Aparna S Chivukula
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Jülich, Germany
| | - Mariia Suslova
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Jülich, Germany
| | - Daniel Kortzak
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Jülich, Germany
| | - Peter Kovermann
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Jülich, Germany
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Jülich, Germany
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27
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Jaudon F, Baldassari S, Musante I, Thalhammer A, Zara F, Cingolani LA. Targeting Alternative Splicing as a Potential Therapy for Episodic Ataxia Type 2. Biomedicines 2020; 8:E332. [PMID: 32899500 PMCID: PMC7555146 DOI: 10.3390/biomedicines8090332] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/01/2020] [Accepted: 09/04/2020] [Indexed: 12/26/2022] Open
Abstract
Episodic ataxia type 2 (EA2) is an autosomal dominant neurological disorder characterized by paroxysmal attacks of ataxia, vertigo, and nausea that usually last hours to days. It is caused by loss-of-function mutations in CACNA1A, the gene encoding the pore-forming α1 subunit of P/Q-type voltage-gated Ca2+ channels. Although pharmacological treatments, such as acetazolamide and 4-aminopyridine, exist for EA2, they do not reduce or control the symptoms in all patients. CACNA1A is heavily spliced and some of the identified EA2 mutations are predicted to disrupt selective isoforms of this gene. Modulating splicing of CACNA1A may therefore represent a promising new strategy to develop improved EA2 therapies. Because RNA splicing is dysregulated in many other genetic diseases, several tools, such as antisense oligonucleotides, trans-splicing, and CRISPR-based strategies, have been developed for medical purposes. Here, we review splicing-based strategies used for genetic disorders, including those for Duchenne muscular dystrophy, spinal muscular dystrophy, and frontotemporal dementia with Parkinsonism linked to chromosome 17, and discuss their potential applicability to EA2.
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Affiliation(s)
- Fanny Jaudon
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy;
| | - Simona Baldassari
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy; (S.B.); (I.M.); (F.Z.)
| | - Ilaria Musante
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy; (S.B.); (I.M.); (F.Z.)
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, 16126 Genoa, Italy
| | - Agnes Thalhammer
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia (IIT), 16132 Genoa, Italy;
- IRCCS Ospedale Policlinico San Martino, 16132 Genoa, Italy
| | - Federico Zara
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, 16147 Genoa, Italy; (S.B.); (I.M.); (F.Z.)
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, 16126 Genoa, Italy
| | - Lorenzo A. Cingolani
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy;
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia (IIT), 16132 Genoa, Italy;
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28
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Giunti P, Mantuano E, Frontali M. Episodic Ataxias: Faux or Real? Int J Mol Sci 2020; 21:ijms21186472. [PMID: 32899446 PMCID: PMC7555854 DOI: 10.3390/ijms21186472] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 11/22/2022] Open
Abstract
The term Episodic Ataxias (EA) was originally used for a few autosomal dominant diseases, characterized by attacks of cerebellar dysfunction of variable duration and frequency, often accompanied by other ictal and interictal signs. The original group subsequently grew to include other very rare EAs, frequently reported in single families, for some of which no responsible gene was found. The clinical spectrum of these diseases has been enormously amplified over time. In addition, episodes of ataxia have been described as phenotypic variants in the context of several different disorders. The whole group is somewhat confused, since a strong evidence linking the mutation to a given phenotype has not always been established. In this review we will collect and examine all instances of ataxia episodes reported so far, emphasizing those for which the pathophysiology and the clinical spectrum is best defined.
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Affiliation(s)
- Paola Giunti
- Laboratory of Neurogenetics, Department of Molecular Neuroscience, UCL Institute of Neurology, London WC2N 5DU, UK
- Correspondence: (P.G.); (M.F.)
| | - Elide Mantuano
- Laboratory of Neurogenetics, Institute of Translational Pharmacology, National Research Council of Italy, 00133 Rome, Italy;
| | - Marina Frontali
- Laboratory of Neurogenetics, Institute of Translational Pharmacology, National Research Council of Italy, 00133 Rome, Italy;
- Correspondence: (P.G.); (M.F.)
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29
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KCND3-Related Neurological Disorders: From Old to Emerging Clinical Phenotypes. Int J Mol Sci 2020; 21:ijms21165802. [PMID: 32823520 PMCID: PMC7461103 DOI: 10.3390/ijms21165802] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/06/2020] [Accepted: 08/11/2020] [Indexed: 12/12/2022] Open
Abstract
KCND3 encodes the voltage-gated potassium ion channel subfamily D member 3, a six trans-membrane protein (Kv4.3), involved in the transient outward K+ current. KCND3 defect causes both cardiological and neurological syndromes. From a neurological perspective, Kv4.3 defect has been associated to SCA type 19/22, a complex neurological disorder encompassing a wide spectrum of clinical features beside ataxia. To better define the phenotypic spectrum and course of KCND3-related neurological disorder, we review the clinical presentation and evolution in 68 reported cases. We delineated two main clinical phenotypes according to the age of onset. Neurodevelopmental disorder with epilepsy and/or movement disorders with ataxia later in the disease course characterized the early onset forms, while a prominent ataxic syndrome with possible cognitive decline, movement disorders, and peripheral neuropathy were observed in the late onset forms. Furthermore, we described a 37-year-old patient with a de novo KCND3 variant [c.901T>C (p.Ser301Pro)], previously reported in dbSNP as rs79821338, and a clinical phenotype paradigmatic of the early onset forms with neurodevelopmental disorder, epilepsy, parkinsonism-dystonia, and ataxia in adulthood, further expanding the clinical spectrum of this condition.
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30
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EAAT1 variants associated with glaucoma. Biochem Biophys Res Commun 2020; 529:943-949. [PMID: 32819603 DOI: 10.1016/j.bbrc.2020.06.099] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 06/21/2020] [Indexed: 11/24/2022]
Abstract
Glaucoma is one of the leading causes of blindness characterized by progressive loss of retinal ganglion cells (RGCs) and their axons. We reported that glutamate/aspartate transporter (GLAST) knockout mice showed progressive RGC loss and optic nerve degeneration that are similar to glaucoma. To explore the possibility that rare variants in the EAAT1 gene (the human homolog of GLAST) cause susceptibility to glaucoma, we performed targeted sequencing of EAAT1 in 440 patients with glaucoma and 450 control subjects. We identified 8 rare variants in 20 out of 440 patients, including 4 synonymous and 4 missense variants located at protein coding regions. One of these rare variants (rs117295512) showed significant association with the risk of glaucoma (OR = 10.44, P = 0.005). Furthermore, the allele frequency for loss-of-function EAAT1 variants, pAla169Gly and pAla329Thr, was 5.5 folds higher in the glaucoma (1.1%) compared with the control cohort (0.2%). These findings suggest that these rare variants may contribute to the pathogenesis of glaucoma and that loss-of-function variants in EAAT1 are present in a small number of patients with glaucoma.
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Inter-Regulation of K v4.3 and Voltage-Gated Sodium Channels Underlies Predisposition to Cardiac and Neuronal Channelopathies. Int J Mol Sci 2020; 21:ijms21145057. [PMID: 32709127 PMCID: PMC7404392 DOI: 10.3390/ijms21145057] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/04/2020] [Accepted: 07/10/2020] [Indexed: 12/13/2022] Open
Abstract
Background: Genetic variants in voltage-gated sodium channels (Nav) encoded by SCNXA genes, responsible for INa, and Kv4.3 channels encoded by KCND3, responsible for the transient outward current (Ito), contribute to the manifestation of both Brugada syndrome (BrS) and spinocerebellar ataxia (SCA19/22). We examined the hypothesis that Kv4.3 and Nav variants regulate each other’s function, thus modulating INa/Ito balance in cardiomyocytes and INa/I(A) balance in neurons. Methods: Bicistronic and other constructs were used to express WT or variant Nav1.5 and Kv4.3 channels in HEK293 cells. INa and Ito were recorded. Results: SCN5A variants associated with BrS reduced INa, but increased Ito. Moreover, BrS and SCA19/22 KCND3 variants associated with a gain of function of Ito, significantly reduced INa, whereas the SCA19/22 KCND3 variants associated with a loss of function (LOF) of Ito significantly increased INa. Auxiliary subunits Navβ1, MiRP3 and KChIP2 also modulated INa/Ito balance. Co-immunoprecipitation and Duolink studies suggested that the two channels interact within the intracellular compartments and biotinylation showed that LOF SCN5A variants can increase Kv4.3 cell-surface expression. Conclusion: Nav and Kv4.3 channels modulate each other’s function via trafficking and gating mechanisms, which have important implications for improved understanding of these allelic cardiac and neuronal syndromes.
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Gawel K, Langlois M, Martins T, van der Ent W, Tiraboschi E, Jacmin M, Crawford AD, Esguerra CV. Seizing the moment: Zebrafish epilepsy models. Neurosci Biobehav Rev 2020; 116:1-20. [PMID: 32544542 DOI: 10.1016/j.neubiorev.2020.06.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/20/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
Zebrafish are now widely accepted as a valuable animal model for a number of different central nervous system (CNS) diseases. They are suitable both for elucidating the origin of these disorders and the sequence of events culminating in their onset, and for use as a high-throughput in vivo drug screening platform. The availability of powerful and effective techniques for genome manipulation allows the rapid modelling of different genetic epilepsies and of conditions with seizures as a core symptom. With this review, we seek to summarize the current knowledge about existing epilepsy/seizures models in zebrafish (both pharmacological and genetic) and compare them with equivalent rodent and human studies. New findings obtained from the zebrafish models are highlighted. We believe that this comprehensive review will highlight the value of zebrafish as a model for investigating different aspects of epilepsy and will help researchers to use these models to their full extent.
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Affiliation(s)
- Kinga Gawel
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway (NCMM), University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway; Department of Experimental and Clinical Pharmacology, Medical University of Lublin, Jaczewskiego St. 8b, 20-090, Lublin, Poland
| | | | - Teresa Martins
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Belval, Luxembourg
| | - Wietske van der Ent
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway (NCMM), University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway
| | - Ettore Tiraboschi
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway (NCMM), University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway; Neurophysics Group, Center for Mind/Brain Sciences, University of Trento, Piazza Manifattura 1, Building 14, 38068, Rovereto, TN, Italy
| | - Maxime Jacmin
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Belval, Luxembourg
| | - Alexander D Crawford
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Belval, Luxembourg; Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Oslo, Norway
| | - Camila V Esguerra
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway (NCMM), University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway.
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Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias. Int J Mol Sci 2020; 21:ijms21103603. [PMID: 32443735 PMCID: PMC7279391 DOI: 10.3390/ijms21103603] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 05/11/2020] [Accepted: 05/13/2020] [Indexed: 12/15/2022] Open
Abstract
Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.
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Chen Y, Wu D, Luo B, Zhao G, Wang K. TGM6 L517W is not a pathogenic variant for spinocerebellar ataxia type 35. NEUROLOGY-GENETICS 2020; 6:e424. [PMID: 32426513 PMCID: PMC7188476 DOI: 10.1212/nxg.0000000000000424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 03/13/2020] [Indexed: 11/15/2022]
Abstract
Objective To investigate the pathogenicity of the TGM6 variant for spinocerebellar ataxia 35 (SCA35), which was previously reported to be caused by pathogenic mutations in the gene TGM6. Methods Neurologic assessment and brain MRI were performed to provide detailed description of the phenotype. Whole-exome sequencing and dynamic mutation analysis were performed to identify the genotype. Results The proband, presenting with myoclonic epilepsy, cognitive decline, and ataxia, harbored both the TGM6 p.L517W variant and expanded CAG repeats in gene ATN1. Further analysis of the other living family members in this pedigree revealed that the CAG repeat number was expanded in all the patients and within normal range in all the unaffected family members. However, the TGM6 p.L517W variant was absent in 2 affected family members, but present in 3 healthy individuals. Conclusions The nonsegregation of the TGM6 variant with phenotype does not support this variant as the disease-causing gene in this pedigree, questioning the pathogenicity of TGM6 in SCA35.
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Affiliation(s)
- Yanxing Chen
- Department of Neurology (Y.C., G.Z.), the Second Affiliated Hospital, School of Medicine, Zhejiang University; and Department of Neurology (D.W., B.L., K.W.), the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Dengchang Wu
- Department of Neurology (Y.C., G.Z.), the Second Affiliated Hospital, School of Medicine, Zhejiang University; and Department of Neurology (D.W., B.L., K.W.), the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Benyan Luo
- Department of Neurology (Y.C., G.Z.), the Second Affiliated Hospital, School of Medicine, Zhejiang University; and Department of Neurology (D.W., B.L., K.W.), the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Guohua Zhao
- Department of Neurology (Y.C., G.Z.), the Second Affiliated Hospital, School of Medicine, Zhejiang University; and Department of Neurology (D.W., B.L., K.W.), the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Kang Wang
- Department of Neurology (Y.C., G.Z.), the Second Affiliated Hospital, School of Medicine, Zhejiang University; and Department of Neurology (D.W., B.L., K.W.), the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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35
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Aagaard Nolting L, Brasch-Andersen C, Cox H, Kanani F, Parker M, Fry AE, Loddo S, Novelli A, Dentici ML, Joss S, Jørgensen JP, Fagerberg CR. A new 1p36.13-1p36.12 microdeletion syndrome characterized by learning disability, behavioral abnormalities, and ptosis. Clin Genet 2020; 97:927-932. [PMID: 32170730 DOI: 10.1111/cge.13739] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 02/28/2020] [Accepted: 03/05/2020] [Indexed: 11/30/2022]
Abstract
Two 1p36 contiguous gene deletion syndromes are known so far: the terminal 1p36 deletion syndrome and a 1p36 deletion syndrome with a critical region located more proximal at 1p36.23-1p36.22. We present even more proximally located overlapping deletions from seven individuals, with the smallest region of overlap comprising 1 Mb at 1p36.13-1p36.12 (chr1:19077793-20081292 (GRCh37/hg19)) defining a new contiguous gene deletion syndrome. The characteristic features of this new syndrome are learning disability or mild intellectual disability, speech delay, behavioral abnormalities, and ptosis. The genes UBR4 and CAPZB are considered the most likely candidate genes for the features of this new syndrome.
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Affiliation(s)
| | | | - Helen Cox
- Clinical Genetics Unit, West Midlands Regional Clinical Genetics Unit Birmingham U.K., Birmingham, UK
| | - Farah Kanani
- Sheffield Clinical Genetics Service, Northern General Hospital, Sheffield, UK
| | - Michael Parker
- Sheffield Clinical Genetics Service, Northern General Hospital, Sheffield, UK
| | - Andrew E Fry
- Institute of Medical Genetics, University Hospital of Wales, Cardiff, UK
| | - Sara Loddo
- Laboratory of Medical Genetics, Bambino Gesù Childrens' Hospital, Rome, Italy
| | - Antonio Novelli
- Laboratory of Medical Genetics, Bambino Gesù Childrens' Hospital, Rome, Italy
| | | | - Shelagh Joss
- Clinical Genetics, West of Scotland Genetic Services, the Queen Elisabeth University Hospital, Glasgow, UK
| | - Joan P Jørgensen
- Hans Christian Andersen Children's Hospital, Odense University Hospital, Odense, Denmark
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36
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Piarroux J, Riant F, Humbertclaude V, Remerand G, Hadjadj J, Rejou F, Coubes C, Pinson L, Meyer P, Roubertie A. FGF14-related episodic ataxia: delineating the phenotype of Episodic Ataxia type 9. Ann Clin Transl Neurol 2020; 7:565-572. [PMID: 32162847 PMCID: PMC7187715 DOI: 10.1002/acn3.51005] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 02/12/2020] [Accepted: 02/14/2020] [Indexed: 11/09/2022] Open
Abstract
We report four patients from two families who presented attacks of childhood-onset episodic ataxia associated with pathogenic mutations in the FGF14 gene. Attacks were triggered by fever, lasted several days, and had variable frequencies. Nystagmus and/or postural tremor and/or learning disabilities were noticed in individuals harboring FGF14 mutation with or without episodic ataxia. These cases and literature data delineate the FGF14-mutation-related episodic ataxia phenotype: wide range of age at onset (from childhood to adulthood), variable durations and frequencies, triggering factors including fever, and association to chronic symptoms. We propose to add FGF14-related episodic ataxia to the list of primary episodic ataxia as Episodic Ataxia type 9.
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Affiliation(s)
- Julie Piarroux
- Département de Neuropédiatrie, CHU Gui de Chauliac, Montpellier, France
| | - Florence Riant
- Service de Génétique Moléculaire Neurovasculaire, Groupe hospitalier Saint-Louis - Lariboisière - Fernand Widal AP-HP, Paris, France
| | - Véronique Humbertclaude
- Service de Médecine Psychologique Enfants et Adolescents, CHU Saint Eloi, Montpellier, France
| | | | - Jessica Hadjadj
- Service de Génétique Moléculaire Neurovasculaire, Groupe hospitalier Saint-Louis - Lariboisière - Fernand Widal AP-HP, Paris, France
| | - Franck Rejou
- Département de Neuropédiatrie, CHU Gui de Chauliac, Montpellier, France
| | - Christine Coubes
- Service de Génétique Clinique, Département de Génétique Médicale, Maladies Rares et Médecine Personnalisée, Hôpital Arnaud de Villeneuve, CHU de Montpellier, Montpellier, France
| | - Lucile Pinson
- Service de Génétique Clinique, Département de Génétique Médicale, Maladies Rares et Médecine Personnalisée, Hôpital Arnaud de Villeneuve, CHU de Montpellier, Montpellier, France
| | - Pierre Meyer
- Département de Neuropédiatrie, CHU Gui de Chauliac, Montpellier, France.,PhyMedExp, U1046 INSERM, UMR9214 CNRS, Montpellier, France
| | - Agathe Roubertie
- Département de Neuropédiatrie, CHU Gui de Chauliac, Montpellier, France.,INSERM U 1051, Institut des Neurosciences de Montpellier, Montpellier, France
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Cerebellar Astrocytes: Much More Than Passive Bystanders In Ataxia Pathophysiology. J Clin Med 2020; 9:jcm9030757. [PMID: 32168822 PMCID: PMC7141261 DOI: 10.3390/jcm9030757] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/06/2020] [Accepted: 03/09/2020] [Indexed: 12/22/2022] Open
Abstract
Ataxia is a neurodegenerative syndrome, which can emerge as a major element of a disease or represent a symptom of more complex multisystemic disorders. It comprises several forms with a highly variegated etiology, mainly united by motor, balance, and speech impairments and, at the tissue level, by cerebellar atrophy and Purkinje cells degeneration. For this reason, the contribution of astrocytes to this disease has been largely overlooked in the past. Nevertheless, in the last few decades, growing evidences are pointing to cerebellar astrocytes as crucial players not only in the progression but also in the onset of distinct forms of ataxia. Although the current knowledge on this topic is very fragmentary and ataxia type-specific, the present review will attempt to provide a comprehensive view of astrocytes’ involvement across the distinct forms of this pathology. Here, it will be highlighted how, through consecutive stage-specific mechanisms, astrocytes can lead to non-cell autonomous neurodegeneration and, consequently, to the behavioral impairments typical of this disease. In light of that, treating astrocytes to heal neurons will be discussed as a potential complementary therapeutic approach for ataxic patients, a crucial point provided the absence of conclusive treatments for this disease.
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Kovermann P, Untiet V, Kolobkova Y, Engels M, Baader S, Schilling K, Fahlke C. Increased glutamate transporter-associated anion currents cause glial apoptosis in episodic ataxia 6. Brain Commun 2020; 2:fcaa022. [PMID: 32954283 PMCID: PMC7425361 DOI: 10.1093/braincomms/fcaa022] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/24/2020] [Accepted: 02/02/2020] [Indexed: 01/08/2023] Open
Abstract
Episodic ataxia type 6 is an inherited neurological condition characterized by combined ataxia and epilepsy. A severe form of this disease with episodes combining ataxia, epilepsy and hemiplegia was recently associated with a proline to arginine substitution at position 290 of the excitatory amino acid transporter 1 in a heterozygous patient. The excitatory amino acid transporter 1 is the predominant glial glutamate transporter in the cerebellum. However, this glutamate transporter also functions as an anion channel and earlier work in heterologous expression systems demonstrated that the mutation impairs the glutamate transport rate, while increasing channel activity. To understand how these changes cause ataxia, we developed a constitutive transgenic mouse model. Transgenic mice display epilepsy, ataxia and cerebellar atrophy and, thus, closely resemble the human disease. We observed increased glutamate-activated chloride efflux in Bergmann glia that triggers the apoptosis of these cells during infancy. The loss of Bergmann glia results in reduced glutamate uptake and impaired neural network formation in the cerebellar cortex. This study shows how gain-of-function of glutamate transporter-associated anion channels causes ataxia through modifying cerebellar development.
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Affiliation(s)
- Peter Kovermann
- Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Verena Untiet
- Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Yulia Kolobkova
- Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Miriam Engels
- Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Stephan Baader
- Anatomisches Institut, Anatomie und Zellbiologie, Rheinische Friedrich-Wilhelm Universität Bonn, 53115 Bonn, Germany
| | - Karl Schilling
- Anatomisches Institut, Anatomie und Zellbiologie, Rheinische Friedrich-Wilhelm Universität Bonn, 53115 Bonn, Germany
| | - Christoph Fahlke
- Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428 Jülich, Germany
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Abstract
Mutations in human PAX6 gene are associated with various congenital eye malformations including aniridia, foveal hypoplasia, and congenital nystagmus. These various phenotypes may depend on the mutation spectrums that can affect DNA-binding affinity, although this hypothesis is debatable. We screened PAX6 mutations in two unrelated patients with congenital nystagmus, and measured DNA-binding affinity through isothermal titration calorimetry (ITC). To elucidate phenotypic differences according to DNA-binding affinity, we also compared DNA-binding affinity among the previously reported PAX6 missense mutations within the linker region between two subdomains of the paired domain (PD). We identified two novel mutations of PAX6 gene: c.214 G > T (p.Gly72Cys) and c.249_250delinsCGC (p.Val84Alafs*8). Both were located within the linker region between the two subdomains of the PD. ITC measurement revealed that the mutation p.Val84Alafs*8 had no DNA-binding affinity, while the p.Gly72Cys mutation showed a decreased binding affinity (Kd = 0.58 μM) by approximately 1.4 times compared to the wild type-PAX6 (Kd = 0.41 μM). We also found that there was no close relationship between DNA-binding affinity and phenotypic differences. Our results suggest that the DNA-binding affinity alone might be insufficient to determine PAX6-related phenotypes, and that other modifier genes or environmental factors might affect phenotypes of the PAX6 gene.
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Tyagi S, Ribera AB, Bannister RA. Zebrafish as a Model System for the Study of Severe Ca V2.1 (α 1A) Channelopathies. Front Mol Neurosci 2020; 12:329. [PMID: 32116539 PMCID: PMC7018710 DOI: 10.3389/fnmol.2019.00329] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 12/23/2019] [Indexed: 02/02/2023] Open
Abstract
The P/Q-type CaV2.1 channel regulates neurotransmitter release at neuromuscular junctions (NMJ) and many central synapses. CACNA1A encodes the pore-containing α1A subunit of CaV2.1 channels. In humans, de novo CACNA1A mutations result in a wide spectrum of neurological, neuromuscular, and movement disorders, such as familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2), as well as a more recently discovered class of more severe disorders, which are characterized by ataxia, hypotonia, cerebellar atrophy, and cognitive/developmental delay. Heterologous expression of CaV2.1 channels has allowed for an understanding of the consequences of CACNA1A missense mutations on channel function. In contrast, a mechanistic understanding of how specific CACNA1A mutations lead in vivo to the resultant phenotypes is lacking. In this review, we present the zebrafish as a model to both study in vivo mechanisms of CACNA1A mutations that result in synaptic and behavioral defects and to screen for effective drug therapies to combat these and other CaV2.1 channelopathies.
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Affiliation(s)
- Sidharth Tyagi
- Medical Scientist Training Program, Yale University School of Medicine, New Haven, CT, United States
| | - Angeles B Ribera
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, United States
| | - Roger A Bannister
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, United States.,Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
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Park Y, Park KW. The Rise of Cerebellar Ataxia in South Korea: 2002–2016. J Clin Neurol 2020; 16:175-176. [PMID: 31942780 PMCID: PMC6974818 DOI: 10.3988/jcn.2020.16.1.175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 10/05/2019] [Accepted: 10/07/2019] [Indexed: 11/17/2022] Open
Affiliation(s)
- YoonAh Park
- Department of Neurology, Kosin University Hospital, Busan, Korea
| | - Kun-Woo Park
- Department of Neurology, Korea University College of Medicine, Seoul, Korea
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Gawel K, Turski WA, van der Ent W, Mathai BJ, Kirstein-Smardzewska KJ, Simonsen A, Esguerra CV. Phenotypic Characterization of Larval Zebrafish (Danio rerio) with Partial Knockdown of the cacna1a Gene. Mol Neurobiol 2019; 57:1904-1916. [PMID: 31875924 PMCID: PMC7118054 DOI: 10.1007/s12035-019-01860-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/15/2019] [Indexed: 12/18/2022]
Abstract
The CACNA1A gene encodes the pore-forming α1 subunit of voltage-gated P/Q type Ca2+ channels (Cav2.1). Mutations in this gene, among others, have been described in patients and rodents suffering from absence seizures and episodic ataxia type 2 with/without concomitant seizures. In this study, we aimed for the first time to assess phenotypic and behavioral alterations in larval zebrafish with partial cacna1aa knockdown, placing special emphasis on changes in epileptiform-like electrographic discharges in larval brains. Whole-mount in situ hybridization analysis revealed expression of cacna1aa in the optic tectum and medulla oblongata of larval zebrafish at 4 and 5 days post-fertilization. Next, microinjection of two antisense morpholino oligomers (individually or in combination) targeting all splice variants of cacna1aa into fertilized zebrafish eggs resulted in dose-dependent mortality and decreased or absent touch response. Over 90% knockdown of cacna1aa on protein level induced epileptiform-like discharges in the optic tectum of larval zebrafish brains. Incubation of morphants with antiseizure drugs (sodium valproate, ethosuximide, lamotrigine, topiramate) significantly decreased the number and, in some cases, cumulative duration of epileptiform-like discharges. In this context, sodium valproate seemed to be the least effective. Carbamazepine did not affect the number and duration of epileptiform-like discharges. Altogether, our data indicate that cacna1aa loss-of-function zebrafish may be considered a new model of absence epilepsy and may prove useful both for the investigation of Cacna1a-mediated epileptogenesis and for in vivo drug screening.
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Affiliation(s)
- Kinga Gawel
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway.,Department of Experimental and Clinical Pharmacology, Medical University of Lublin, Jaczewskiego St. 8b, 20-090, Lublin, Poland
| | - Waldemar A Turski
- Department of Experimental and Clinical Pharmacology, Medical University of Lublin, Jaczewskiego St. 8b, 20-090, Lublin, Poland
| | - Wietske van der Ent
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway
| | - Benan J Mathai
- Faculty of Medicine, Institute of Basic Medical Sciences and Centre for Cancer Cell Reprogramming, Institute of Clinical Medicine, University of Oslo, 1112 Blindern, 0317, Oslo, Norway
| | - Karolina J Kirstein-Smardzewska
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway
| | - Anne Simonsen
- Faculty of Medicine, Institute of Basic Medical Sciences and Centre for Cancer Cell Reprogramming, Institute of Clinical Medicine, University of Oslo, 1112 Blindern, 0317, Oslo, Norway
| | - Camila V Esguerra
- Chemical Neuroscience Group, Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Gaustadalléen 21, Forskningsparken, 0349, Oslo, Norway. .,School of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Sem Sælandsvei 24, 0371, Oslo, Norway.
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Schesny M, Joncourt F, Tarnutzer AA. Acetazolamide-Responsive Episodic Ataxia Linked to Novel Splice Site Variant in FGF14 Gene. THE CEREBELLUM 2019; 18:649-653. [PMID: 30607796 DOI: 10.1007/s12311-018-0997-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Here we describe the case of a patient with episodic dizziness and gait imbalance for 7 years and a negative family history. On clinical examination, interictally, the patient presented with gaze-evoked nystagmus and rebound nystagmus and slight dysarthria. MRI of the brain was normal and peripheral-vestibular function was bilaterally intact. Based on genetic testing (episodic ataxia panel), a heterozygote splice site variant in intron 1 of the FGF14 gene was identified. This report adds important new evidence to previous observations that pathogenic variants in the FGF14 gene may result in variable phenotypes, either in progressive spinocerebellar ataxia (type 27) or in episodic ataxia as in our case. Our patient responded well to acetazolamide (reduction in the frequency of attacks by about two thirds), supporting the hypothesis of a sodium channelopathy.
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Affiliation(s)
- M Schesny
- Department of Neurology, University Hospital Zurich, Frauenklinikstr. 26, 8091, Zurich, Switzerland
| | - F Joncourt
- Division of Human Genetics, Department of Pediatrics, University Hospital Berne, Berne, Switzerland
| | - Alexander A Tarnutzer
- Department of Neurology, University Hospital Zurich, Frauenklinikstr. 26, 8091, Zurich, Switzerland. .,University of Zurich, Zurich, Switzerland.
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Hsiao CT, Fu SJ, Liu YT, Lu YH, Zhong CY, Tang CY, Soong BW, Jeng CJ. Novel SCA19/22-associated KCND3 mutations disrupt human K V 4.3 protein biosynthesis and channel gating. Hum Mutat 2019; 40:2088-2107. [PMID: 31293010 DOI: 10.1002/humu.23865] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 07/05/2019] [Accepted: 07/07/2019] [Indexed: 11/07/2022]
Abstract
Mutations in the human voltage-gated K+ channel subunit KV 4.3-encoding KCND3 gene have been associated with the autosomal dominant neurodegenerative disorder spinocerebellar ataxia types 19 and 22 (SCA19/22). The precise pathophysiology underlying the dominant inheritance pattern of SCA19/22 remains elusive. Using cerebellar ataxia-specific targeted next-generation sequencing technology, we identified two novel KCND3 mutations, c.950 G>A (p.C317Y) and c.1123 C>T (p.P375S) from a cohort with inherited cerebellar ataxias in Taiwan. The patients manifested notable phenotypic heterogeneity that includes cognitive impairment. We employed in vitro heterologous expression systems to inspect the biophysical and biochemical properties of human KV 4.3 harboring the two novel mutations, as well as two previously reported but uncharacterized disease-related mutations, c.1013 T>A (p.V338E) and c.1130 C>T (p.T377M). Electrophysiological analyses revealed that all of these SCA19/22-associated KV 4.3 mutant channels manifested loss-of-function phenotypes. Protein chemistry and immunofluorescence analyses further demonstrated that these mutants displayed enhanced protein degradation and defective membrane trafficking. By coexpressing KV 4.3 wild-type with the disease-related mutants, we provided direct evidence showing that the mutants instigated anomalous protein biosynthesis and channel gating of KV 4.3. We propose that the dominant inheritance pattern of SCA19/22 may be explained by the dominant-negative effects of the mutants on protein biosynthesis and voltage-dependent gating of KV 4.3 wild-type channel.
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Affiliation(s)
- Cheng-Tsung Hsiao
- Department of Internal Medicine, Taipei Veterans General Hospital Taoyuan Branch, Taoyuan, Taiwan
- Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan
- Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
- Department of Neurology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Ssu-Ju Fu
- Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Yo-Tsen Liu
- Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan
- Department of Neurology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Yi-Hsiang Lu
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Ciao-Yu Zhong
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Chih-Yung Tang
- Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Bing-Wen Soong
- Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan
- Brain Research Center, National Yang-Ming University, Taipei, Taiwan
- Department of Neurology, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan
- Taipei Neuroscience Institute, Taipei Medical University, Taipei, Taiwan
| | - Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
- Brain Research Center, National Yang-Ming University, Taipei, Taiwan
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Miura S, Kosaka K, Fujioka R, Uchiyama Y, Shimojo T, Morikawa T, Irie A, Taniwaki T, Shibata H. Spinocerebellar ataxia 27 with a novel nonsense variant (Lys177X) in FGF14. Eur J Med Genet 2019; 62:172-176. [DOI: 10.1016/j.ejmg.2018.07.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 07/09/2018] [Indexed: 12/22/2022]
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Jung I, Kim JS. Abnormal Eye Movements in Parkinsonism and Movement Disorders. J Mov Disord 2019; 12:1-13. [PMID: 30732429 PMCID: PMC6369379 DOI: 10.14802/jmd.18034] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 12/12/2018] [Indexed: 01/10/2023] Open
Abstract
Abnormal eye movements are commonly observed in movement disorders. Ocular motility examination should include bedside evaluation and laboratory recording of ocular misalignment, involuntary eye movements, including nystagmus and saccadic intrusions/oscillations, triggered nystagmus, saccades, smooth pursuit (SP), and the vestibulo-ocular reflex. Patients with Parkinson’s disease (PD) mostly show hypometric saccades, especially for the self-paced saccades, and impaired SP. Early vertical saccadic palsy is characteristic of progressive supranuclear palsy-Richardson’s syndrome. Patients with cortico-basal syndrome typically show a delayed onset of saccades. Downbeat and gaze-evoked nystagmus and hypermetric saccades are characteristic ocular motor findings in ataxic disorders due to cerebellar dysfunction. In this review, we discuss various ocular motor findings in movement disorders, including PD and related disorders, ataxic syndromes, and hyperkinetic movement disorders. Systemic evaluation of the ocular motor functions may provide valuable information for early detection and monitoring of movement disorders, despite an overlap in the abnormal eye movements among different movement disorders.
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Affiliation(s)
- Ileok Jung
- Department of Neurology, Korea University College of Medicine, Korea University Ansan Hospital, Ansan, Korea
| | - Ji-Soo Kim
- Department of Neurology, Seoul National University College of Medicine, Seoul, Korea,Dizziness Center, Clinical Neuroscience Center, and Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea
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Min R, van der Knaap MS. Genetic defects disrupting glial ion and water homeostasis in the brain. Brain Pathol 2019; 28:372-387. [PMID: 29740942 PMCID: PMC8028498 DOI: 10.1111/bpa.12602] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 03/02/2018] [Indexed: 12/23/2022] Open
Abstract
Electrical activity of neurons in the brain, caused by the movement of ions between intracellular and extracellular compartments, is the basis of all our thoughts and actions. Maintaining the correct ionic concentration gradients is therefore crucial for brain functioning. Ion fluxes are accompanied by the displacement of osmotically obliged water. Since even minor brain swelling leads to severe brain damage and even death, brain ion and water movement has to be tightly regulated. Glial cells, in particular astrocytes, play a key role in ion and water homeostasis. They are endowed with specific channels, pumps and carriers to regulate ion and water flow. Glial cells form a large panglial syncytium to aid the uptake and dispersal of ions and water, and make extensive contacts with brain fluid barriers for disposal of excess ions and water. Genetic defects in glial proteins involved in ion and water homeostasis disrupt brain functioning, thereby leading to neurological diseases. Since white matter edema is often a hallmark disease feature, many of these diseases are characterized as leukodystrophies. In this review we summarize our current understanding of inherited glial diseases characterized by disturbed brain ion and water homeostasis by integrating findings from MRI, genetics, neuropathology and animal models for disease. We discuss how mutations in different glial proteins lead to disease, and highlight the similarities and differences between these diseases. To come to effective therapies for this group of diseases, a better mechanistic understanding of how glial cells shape ion and water movement in the brain is crucial.
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Affiliation(s)
- Rogier Min
- Department of Child Neurology, Amsterdam Neuroscience, VU University Medical Center, Amsterdam, The Netherlands.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, VU University, Amsterdam, The Netherlands
| | - Marjo S van der Knaap
- Department of Child Neurology, Amsterdam Neuroscience, VU University Medical Center, Amsterdam, The Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, VU University, Amsterdam, The Netherlands
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Fung JLF, Tsang MHY, Leung GKC, Yeung KS, Mak CCY, Fung CW, Chan SHS, Yu MHC, Chung BHY. A significant inflation in TGM6 genetic risk casts doubt in its causation in spinocerebellar ataxia type 35. Parkinsonism Relat Disord 2019; 63:42-45. [PMID: 30670339 DOI: 10.1016/j.parkreldis.2019.01.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/28/2018] [Accepted: 01/13/2019] [Indexed: 11/19/2022]
Abstract
Spinocerebellar ataxia 35 (SCA35) has been associated with pathogenic mutations in the gene TGM6. In a Chinese exome sequencing cohort, we identified 8 families with reported TGM6 variants sharing no features of SCA35. Considering this finding, we reviewed the public database gnomAD and found these variants to be significantly more common in the East Asians than in other ethnic groups (P < 0.0001). Gene constraint metrics showed that both missense and loss-of-function variants in TGM6 are likely to be tolerated and there is no regional constraint. By performing inflation analysis, it demonstrated that the cumulative frequency of TGM6 reported pathogenic variants is at least 111-fold inflated over disease prevalence of all autosomal dominant SCAs, indicating a high chance of misdiagnosis or low penetrance. Misclassification of benign or low penetrant variants as pathogenic is a significant problem that often results in genetic misdiagnosis. This highlights the necessity of evaluating variant pathogenicity with sequencing of genomes from diverse populations, both from asymptomatic controls and phenotypically different patients, in order to ensure accurate classification of variants.
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Affiliation(s)
- Jasmine L F Fung
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Mandy H Y Tsang
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Gordon K C Leung
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Kit San Yeung
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Christopher C Y Mak
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Cheuk Wing Fung
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Sophelia H S Chan
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Mullin H C Yu
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
| | - Brian H Y Chung
- Department of Paediatric and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
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Abstract
Primary episodic ataxias (EAs) are a group of dominantly inherited disorders characterized by transient recurrent incoordination and truncal instability, often triggered by physical exertion and emotional stress, variably associated with progressive baseline ataxia. There are now eight designated subtypes based largely on genetic loci. Mutations have been identified in multiple individuals and families with EA1, EA2, and EA6, mostly with onset before adulthood. EA1 and EA2 are prototypical neurologic channelopathies. EA1 is caused by heterozygous mutations in KCNA1, which encodes the α1 subunit of a neuronal voltage-gated potassium channel, Kv1.1. EA2, the most common and best characterized, is caused by heterozygous mutations in CACNA1A, which encodes the α1A subunit of a neuronal voltage-gated calcium channel, Cav2.1. EA6 is caused by heterozygous mutations in SLC1A3, which encodes a subunit of a glial excitatory amino acid transporter, EAAT1. The other EA subtypes were defined in single families awaiting gene identification and further confirmation. This chapter focuses on the best-characterized EA syndromes, the clinical assessment and genetic diagnosis of EA, and the management of EA, as well as newly recognized allelic disorders that have greatly expanded the clinical spectrum of EA2. Illustrative cases are discussed, with a focus on sporadic patients with congenital features without episodic ataxia who present diagnostic and therapeutic challenges.
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Affiliation(s)
- Joanna C Jen
- Departments of Neurology, Otolaryngology, and Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, United States.
| | - Jijun Wan
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, United States
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