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Sena LS, Lemes RB, Furtado GV, Saraiva-Pereira ML, Jardim LB. A model for the dynamics of expanded CAG repeat alleles: ATXN2 and ATXN3 as prototypes. Front Genet 2023; 14:1296614. [PMID: 38034492 PMCID: PMC10682950 DOI: 10.3389/fgene.2023.1296614] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/27/2023] [Indexed: 12/02/2023] Open
Abstract
Background: Spinocerebellar ataxia types 2 (SCA2) and 3 (SCA3/MJD) are diseases due to dominant unstable expansions of CAG repeats (CAGexp). Age of onset of symptoms (AO) correlates with the CAGexp length. Repeat instability leads to increases in the expanded repeats, to important AO anticipations and to the eventual extinction of lineages. Because of that, compensatory forces are expected to act on the maintenance of expanded alleles, but they are poorly understood. Objectives: we described the CAGexp dynamics, adapting a classical equation and aiming to estimate for how many generations will the descendants of a de novo expansion last. Methods: A mathematical model was adapted to encompass anticipation, fitness, and allelic segregation; and empirical data fed the model. The arbitrated ancestral mutations included in the model had the lowest CAGexp and the highest AO described in the literature. One thousand generations were simulated until the alleles were eliminated, fixed, or 650 generations had passed. Results: All SCA2 lineages were eliminated in a median of 10 generations. In SCA3/MJD lineages, 593 were eliminated in a median of 29 generations. The other ones were eliminated due to anticipation after the 650th generation or remained indefinitely with CAG repeats transitioning between expanded and unexpanded ranges. Discussion: the model predicted outcomes compatible with empirical data - the very old ancestral SCA3/MJD haplotype, and the de novo SCA2 expansions -, which previously seemed to be contradictory. This model accommodates these data into understandable dynamics and might be useful for other CAGexp disorders.
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Affiliation(s)
- Lucas Schenatto Sena
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | | | - Gabriel Vasata Furtado
- Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Maria Luiza Saraiva-Pereira
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Laura Bannach Jardim
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Departamento de Medicina Interna, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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Sena LS, Dos Santos Pinheiro J, Hasan A, Saraiva-Pereira ML, Jardim LB. Spinocerebellar ataxia type 2 from an evolutionary perspective: Systematic review and meta-analysis. Clin Genet 2021; 100:258-267. [PMID: 33960424 DOI: 10.1111/cge.13978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/19/2021] [Accepted: 05/05/2021] [Indexed: 01/27/2023]
Abstract
Dominant diseases due to expanded CAG repeat tracts, such as spinocerebellar ataxia type 2 (SCA2), are prone to anticipation and worsening of clinical picture in subsequent generations. There is insufficient data about selective forces acting on the maintenance of these diseases in populations. We made a systematic review and meta-analysis on the effect of the CAG length over age at onset, instability of transmissions, anticipation, de novo or sporadic cases, fitness, segregation of alleles, and ancestral haplotypes. The correlation between CAG expanded and age at onset was r2 = 0.577, and transmission of the mutant allele was associated with an increase of 2.42 CAG repeats in the next generation and an anticipation of 14.62 years per generation, on average. One de novo and 18 sporadic cases were detected. Affected SCA2 individuals seem to have more children than controls. The expanded allele was less segregated than the 22-repeat allele in children of SCA2 subjects. Several ancestral SCA2 haplotypes were published. Data suggest that SCA2 lineages may tend to disappear eventually, due to strong anticipation phenomena. Whether or not the novel cases come from common haplotypes associated with a predisposition to further expansions is a question that needs to be addressed by future studies.
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Affiliation(s)
- Lucas Schenatto Sena
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Jordânia Dos Santos Pinheiro
- Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil.,Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Ali Hasan
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Maria Luiza Saraiva-Pereira
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil.,Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Instituto de Genética Médica Populacional, Porto Alegre, Brazil.,Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Laura Bannach Jardim
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Centros de Pesquisa Clínica e Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil.,Instituto de Genética Médica Populacional, Porto Alegre, Brazil.,Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil.,Departamento de Medicina Interna, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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Rodríguez-Labrada R, Martins AC, Magaña JJ, Vazquez-Mojena Y, Medrano-Montero J, Fernandez-Ruíz J, Cisneros B, Teive H, McFarland KN, Saraiva-Pereira ML, Cerecedo-Zapata CM, Gomez CM, Ashizawa T, Velázquez-Pérez L, Jardim LB. Founder Effects of Spinocerebellar Ataxias in the American Continents and the Caribbean. THE CEREBELLUM 2021; 19:446-458. [PMID: 32086717 DOI: 10.1007/s12311-020-01109-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Spinocerebellar ataxias (SCAs) comprise a heterogeneous group of autosomal dominant disorders. The relative frequency of the different SCA subtypes varies broadly among different geographical and ethnic groups as result of genetic drifts. This review aims to provide an update regarding SCA founders in the American continents and the Caribbean as well as to discuss characteristics of these populations. Clusters of SCAs were detected in Eastern regions of Cuba for SCA2, in South Brazil for SCA3/MJD, and in Southeast regions of Mexico for SCA7. Prevalence rates were obtained and reached 154 (municipality of Báguano, Cuba), 166 (General Câmara, Brazil), and 423 (Tlaltetela, Mexico) patients/100,000 for SCA2, SCA3/MJD, and SCA7, respectively. In contrast, the scattered families with spinocerebellar ataxia type 10 (SCA10) reported all over North and South Americas have been associated to a common Native American ancestry that may have risen in East Asia and migrated to Americas 10,000 to 20,000 years ago. The comprehensive review showed that for each of these SCAs corresponded at least the development of one study group with a large production of scientific evidence often generalizable to all carriers of these conditions. Clusters of SCA populations in the American continents and the Caribbean provide unusual opportunity to gain insights into clinical and genetic characteristics of these disorders. Furthermore, the presence of large populations of patients living close to study centers can favor the development of meaningful clinical trials, which will impact on therapies and on quality of life of SCA carriers worldwide.
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Affiliation(s)
| | - Ana Carolina Martins
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, 91540-070, Brazil
| | - Jonathan J Magaña
- Department of Genetics, Laboratory of Genomic Medicine, National Rehabilitation Institute (INR-LGII), 14389, Mexico City, Mexico
| | - Yaimeé Vazquez-Mojena
- Centre for the Research and Rehabilitation of Hereditary Ataxias, 80100, Holguín, Cuba
| | | | - Juan Fernandez-Ruíz
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, 04510, Mexico City, Mexico
| | - Bulmaro Cisneros
- Department of Genetics and Molecular Biology, Center of Research and Advanced Studies (CINVESTAV-IPN), 07360, Mexico City, Mexico
| | - Helio Teive
- Movement Disorders Unit, Neurology Service, Internal Medicine Department, Hospital de Clínicas Federal University of Paraná, Curitiba, PR, 80240-440, Brazil
| | | | - Maria Luiza Saraiva-Pereira
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, 91540-070, Brazil
- Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, 90035-903, Brazil
- Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, 90035-903, Brazil
| | - César M Cerecedo-Zapata
- Department of Genetics, Laboratory of Genomic Medicine, National Rehabilitation Institute (INR-LGII), 14389, Mexico City, Mexico
- Rehabilitation and Social Inclusion Center of Veracruz (CRIS-DIF), Xalapa, 91070, Veracruz, Mexico
| | | | - Tetsuo Ashizawa
- Program of Neuroscience, Houston Methodist Research Institute, Houston, TX, 77030, USA
| | - Luis Velázquez-Pérez
- Centre for the Research and Rehabilitation of Hereditary Ataxias, 80100, Holguín, Cuba.
- Cuban Academy of Sciences, 10100, La Havana, Cuba.
| | - Laura Bannach Jardim
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, 91540-070, Brazil
- Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, 90035-903, Brazil
- Departamento de Medicina Interna, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, 90035-903, Brazil
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4
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Vieira TA, Trapp FB, de Souza CFM, Faccini LS, Jardim LB, Schwartz IVD, Riegel M, Vargas CR, Burin MG, Leistner-Segal S, Ashton-Prolla P, Giugliani R. Information and Diagnosis Networks - tools to improve diagnosis and treatment for patients with rare genetic diseases. Genet Mol Biol 2019; 42:155-164. [PMID: 31188934 PMCID: PMC6687351 DOI: 10.1590/1678-4685-gmb-2018-0214] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 12/12/2018] [Indexed: 12/14/2022] Open
Abstract
Brazil is a country of continental dimensions and most genetic services are concentrated in the Southeast and South, including the Medical Genetics Service of the Hospital de Clínicas de Porto Alegre (MGS/HCPA). As many areas on the country do not have adequate medical genetics support, networks were designed to extend the service of the MGS/HCPA reference center. This paper presents the information and diagnosis networks that have their headquarters at MGS/HCPA: SIAT (National Information System on Teratogenic Agents), SIEM (Information Service on Inborn Errors of Metabolism), Alô Genética (Hello Genetics - Medical Genetics Information Service for Primary Health Care Professionals); Rede MPS Brasil (MPS-Mucopolysaccharidosis Brazil Network); Rede EIM Brasil (IEM-Inborn Errors of Metabolism Brazil Network), Rede NPC Brasil (Niemann-Pick C - NPC Brazil Network), Rede DLD Brasil (LSD-Lysosomal Storage Disorders Brazil Network), Rede DXB (MSUD-Maple Syrup Urine Disease Network), RedeBRIM (Brazilian Network of Reference and Information in Microdeletion Syndromes Project), Rede Neurogenética (Neurogenetics Network), and Rede Brasileira de Câncer Hereditário (Brazilian Hereditary Cancer Network). These tools are very useful to provide access to a qualified information and/or diagnostic service for specialized and non-specialized health services, bypassing difficulties that preclude patients to access reference centers.
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Affiliation(s)
- Taiane Alves Vieira
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Research and Postgraduate Group - Hospital de Clinicas de
Porto Alegre, Porto Alegre, RS, Brazil
| | | | | | - Lavínia Schuler Faccini
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Department of Genetics – Universidade Federal do Rio Grande do
Sul, Porto Alegre, RS, Brazil
| | - Laura Bannach Jardim
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Department of Internal Medicine - Universidade Federal do Rio
Grande do Sul, Porto Alegre, RS, Brazil
| | - Ida Vanessa Doederlein Schwartz
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Department of Genetics – Universidade Federal do Rio Grande do
Sul, Porto Alegre, RS, Brazil
| | - Mariluce Riegel
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
| | - Carmen Regla Vargas
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
| | - Maira Graeff Burin
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
| | - Sandra Leistner-Segal
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
| | - Patrícia Ashton-Prolla
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Research and Postgraduate Group - Hospital de Clinicas de
Porto Alegre, Porto Alegre, RS, Brazil
- Department of Genetics – Universidade Federal do Rio Grande do
Sul, Porto Alegre, RS, Brazil
| | - Roberto Giugliani
- Medical Genetics Service, Hospital de Clinicas de Porto
Alegre, Porto Alegre, RS, Brazil
- Department of Genetics – Universidade Federal do Rio Grande do
Sul, Porto Alegre, RS, Brazil
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5
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Chen Z, Sequeiros J, Tang B, Jiang H. Genetic modifiers of age-at-onset in polyglutamine diseases. Ageing Res Rev 2018; 48:99-108. [PMID: 30355507 DOI: 10.1016/j.arr.2018.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 08/03/2018] [Accepted: 10/17/2018] [Indexed: 11/25/2022]
Abstract
Polyglutamine (polyQ) diseases are a group of clinically and genetically heterogeneous neurodegenerative diseases. Expansion size correlates with age-at-onset (AO) and severity, and shows a critical threshold for each polyQ disease. Although an expanded CAG tract is sufficient to trigger disease, not all variation in AO is explained by (CAG)n length, which suggests the contribution of other modifying factors. Methods used to identify genetic modifiers in polyQ diseases have progressed from candidate genes to unbiased genome-wide searches. Inconsistency of results from candidate-genes studies are partly explained by sample size, study design and variable population frequency of "polymorphisms"; a genome-wide search may help elucidating more precise disease mechanisms underlying specific interaction networks. We review known genetic modifiers for polyQ diseases, and discuss developing strategies to find modulation, from common variants to networks disclosing small cumulative effects of key genes and modifying pathways. This may lead to a better understanding of genotype-phenotype correlation and the proposal of new potential targets for therapeutical interventions.
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Yau WY, O'Connor E, Sullivan R, Akijian L, Wood NW. DNA repair in trinucleotide repeat ataxias. FEBS J 2018; 285:3669-3682. [PMID: 30152109 DOI: 10.1111/febs.14644] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/15/2018] [Accepted: 08/23/2018] [Indexed: 12/21/2022]
Abstract
The inherited cerebellar ataxias comprise of a genetic heterogeneous group of disorders. Pathogenic expansions of cytosine-adenine-guanine (CAG) encoding polyglutamine tracts account for the largest proportion of autosomal dominant cerebellar ataxias, while GAA expansion in the first introns of frataxin gene is the commonest cause of autosomal recessive cerebellar ataxias. Currently, there is no available treatment to alter the disease trajectory, with devastating consequences for affected individuals. Inter- and Intrafamily phenotypic variability suggest the existence of genetic modifiers, which may become targets amendable to treatment. Recent studies have demonstrated the importance of DNA repair pathways in modifying spinocerebellar ataxia with CAG repeat expansions. In this review, we discuss the mechanisms in which DNA repair pathways, epigenetics and other genetic factors may act as modifiers in cerebellar ataxias due to trinucleotide repeat expansions.
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Affiliation(s)
- Wai Yan Yau
- Department of Molecular Neuroscience, Institute of Neurology, University College London, UK
| | - Emer O'Connor
- Department of Molecular Neuroscience, Institute of Neurology, University College London, UK
| | - Roisin Sullivan
- Department of Molecular Neuroscience, Institute of Neurology, University College London, UK
| | - Layan Akijian
- Department of Neurology, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Nicholas W Wood
- Department of Molecular Neuroscience, Institute of Neurology, University College London, UK.,Neurogenetics laboratory, The National Hospital for Neurology and Neurosurgery, London, UK
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Wang XZ, Huang XY, Yao JG, Wang C, Xia Q, Long XD. Genetic polymorphisms in ataxin-3 and liver cirrhosis risk related to aflatoxin B1. Oncotarget 2018; 9:27321-27332. [PMID: 29937988 PMCID: PMC6007954 DOI: 10.18632/oncotarget.24535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/07/2017] [Indexed: 01/17/2023] Open
Abstract
Background Altered expression of ataxin-3 (AT3) can modify DNA repair capacity and is observed in human diseases. The genetic polymorphisms of this gene in aflatoxin B1 (AFB1)–related liver cirrhosis (LC) have not yet been elucidated. Materials and Methods We conducted a hospital-based case–control study, including 384 patients with LC and 851 controls without any liver diseases, to assess the association between 264 polymorphisms in AT3 and AFB1-related LC risk. Genotype were tested using TaqMan-PCR or sequencing technique. Results We found three differentially distributed SNPs (rs8021276, rs7158733, and rs10146249) via the screening analysis; however, only rs8021276 polymorphism was further identified to modify the risk of LC. Compared with the homozygote of rs8021276 A alleles (rs8021276-AA), the genotypes of rs8021276 G alleles (rs8021276-AG or -GG) increased LC risk (OR: 2.48 and 6.98; 95% CI: 1.84–3.33 and 4.35–11.22, respectively). Significant interactive effects between risk genotypes and AFB1 exposure status were also observed in the joint effects analysis. Additionally, rs8021276 polymorphism was also associated with down-regulation of AT3 mRNA expression and increasing AFB1-DNA adducts in liver tissues with cirrhosis. Conclusions These results suggest AT3 polymorphisms may be risk biomarkers of AFB1-related LC, and rs8021276 is a potential candidate.
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Affiliation(s)
- Xing-Zhizi Wang
- Department of Pathology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China
| | - Xiao-Ying Huang
- Department of Pathology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China
| | - Jin-Guang Yao
- Department of Pathology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China
| | - Chao Wang
- Department of Digestive Medicine, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China
| | - Qiang Xia
- Department of Liver Surgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Xi-Dai Long
- Department of Pathology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China.,Department of Liver Surgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China.,Guangxi Clinic Research Center of Hepatobiliary Diseases, Baise 533000, China
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Neurological phenotypes in spinocerebellar ataxia type 2: Role of mitochondrial polymorphism A10398G and other risk factors. Parkinsonism Relat Disord 2017. [PMID: 28648514 DOI: 10.1016/j.parkreldis.2017.06.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Spinocerebellar ataxia type 2 (SCA2) is due to a CAG expansion (CAGexp) at ATXN2. SCA2 presents great clinical variability, alongside characteristic ataxia with saccadic slowness. AIMS To study parkinsonism, dementia, dystonia, and amyotrophy as subphenotypes of SCA2, and to explore the effect of CAG repeats at different loci and of mitochondrial polymorphism A10398G as modifiers of phenotype. METHODS Symptomatic subjects were classified by presence/absence of neurological signs mentioned above; SARA and NESSCA scores were obtained. CAG repeats at ATXN1, ATXN2, ATXN3, CACNA1A, ATXN7 and RAI1, and polymorphism A10398G at mtDNA were established. Group characteristics were compared, with a p < 0.05. RESULTS Forty-eight SCA2 individuals were included. Age at onset, CAGexp, and disease duration explained 53% and 43% of SARA and NESSCA variations, respectively. CAGexp of subjects with and without parkinsonism were different (medians of 42 and 39 repeats) as well as of subjects with and without dystonia (44 and 40 repeats). Amyotrophy was not significantly related to any variable under study. Concerning polymorphism A10398G, 83% of subjects with and 34% of those without cognitive decline carried 10398G at (p = 0.003). DISCUSSION Treating the four phenotypic subgroups as outcomes was a valid strategy to identify modifiers of disease. Among correlations found, some confirmed previous reports, such as that between dystonia and CAGexp. Of note was the association between cognitive decline and the variant G at mitochondrial polymorphism A10398G, a variant formerly related to earlier ages at onset in SCA2.
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