1
|
Sharma P, Sonakar AK, Tyagi N, Suroliya V, Kumar M, Kutum R, Asokchandran V, Ambawat S, Shamim U, Anand A, Ahmad I, Shakya S, Uppili B, Mathur A, Parveen S, Jain S, Singh J, Seth M, Zahra S, Joshi A, Goel D, Sahni S, Kamai A, Wadhwa S, Murali A, Saifi S, Chowdhury D, Pandey S, Anand KS, Narasimhan RL, Laskar S, Kushwaha S, Kumar M, Shaji CV, Srivastava MVP, Srivastava AK, Faruq M. Genetics of Ataxias in Indian Population: A Collative Insight from a Common Genetic Screening Tool. ADVANCED GENETICS (HOBOKEN, N.J.) 2022; 3:2100078. [PMID: 36618024 PMCID: PMC9744545 DOI: 10.1002/ggn2.202100078] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Indexed: 01/11/2023]
Abstract
Cerebellar ataxias (CAs) represent a group of autosomal dominant and recessive neurodegenerative disorders affecting cerebellum with or without spinal cord. Overall, CAs have preponderance for tandem nucleotide repeat expansions as an etiological factor (10 TREs explain nearly 30-40% of ataxia cohort globally). The experience of 10 years of common genetic ataxia subtypes for ≈5600 patients' referrals (Pan-India) received at a single center is shared herein. Frequencies (in %, n) of SCA types and FRDA in the sample cohort are observed as follows: SCA12 (8.6%, 490); SCA2 (8.5%, 482); SCA1 (4.8%, 272); SCA3 (2%, 113); SCA7 (0.5%, 28); SCA6 (0.1%, 05); SCA17 (0.1%, 05), and FRDA (2.2%, 127). A significant amount of variability in TRE lengths at each locus is observed, we noted presence of biallelic expansion, co-occurrence of SCA-subtypes, and the presence of premutable normal alleles. The frequency of mutated GAA-FRDA allele in healthy controls is 1/158 (0.63%), thus an expected FRDA prevalence of 1:100 000 persons. The data of this study are relevant not only for clinical decision making but also for guidance in direction of genetic investigations, transancestral comparison of genotypes, and lastly provide insight for policy decision for the consideration of SCAs under rare disease category.
Collapse
Affiliation(s)
- Pooja Sharma
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | | | - Nishu Tyagi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Varun Suroliya
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Manish Kumar
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Rintu Kutum
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Vivekananda Asokchandran
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Sakshi Ambawat
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Uzma Shamim
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Avni Anand
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Ishtaq Ahmad
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Sunil Shakya
- Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Bharathram Uppili
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aradhana Mathur
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shaista Parveen
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shweta Jain
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Jyotsna Singh
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Neurology DepartmentNeuroscience CentreNew Delhi110029India
| | - Malika Seth
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Sana Zahra
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aditi Joshi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Divya Goel
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Shweta Sahni
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Asangla Kamai
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Saruchi Wadhwa
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | - Aparna Murali
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | - Sheeba Saifi
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India
| | | | - Sanjay Pandey
- Department of NeurologyGB Pant HospitalDelhi110002India
| | - Kuljeet Singh Anand
- Department of NeurologyPost Graduate Institute of Medical Education and ResearchDr. Ram Manohar Lohia HospitalNew Delhi110001India
| | | | | | - Suman Kushwaha
- Department of NeurologyInstitute of Human Behaviour and Allied SciencesDelhi110095India
| | | | | | | | | | - Mohammed Faruq
- Genomics and Molecular MedicineCSIR‐Institute of Genomics and Integrative Biology (CSIR‐IGIB)Mall RoadDelhi110007India,Academy for Scientific and Innovative ResearchGhaziabadUttar Pradesh201002India
| | | |
Collapse
|
2
|
Sena LS, Dos Santos Pinheiro J, Saraiva-Pereira ML, Jardim LB. Selective forces acting on spinocerebellar ataxia type 3/Machado-Joseph disease recurrency: A systematic review and meta-analysis. Clin Genet 2020; 99:347-358. [PMID: 33219521 DOI: 10.1111/cge.13888] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/25/2020] [Accepted: 11/17/2020] [Indexed: 12/22/2022]
Abstract
Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is a dominant neurodegenerative disease caused by the expansion of a CAG repeat tract in ATXN3. Anticipation and worsening of clinical picture in subsequent generations were repeatedly reported, but there is no indication that SCA3/MJD frequency is changing. Thus, we performed a systematic review and meta-analysis on phenomena with potential effect on SCA3/MJD recurrency in populations: instability of CAG repeat transmissions, anticipation, fitness, and segregation of alleles. Transmission of the mutant allele was associated with an increase of 1.23 CAG repeats in the next generation, and the average change in age at onset showed an anticipation of 7.75 years per generation; but biased recruitments cannot be ruled out. Affected SCA3/MJD individuals had 45% more children than related controls. Transmissions from SCA3/MJD carriers showed that the expanded allele was segregated in 64% of their children. In contrast, transmissions from normal subjects showed that the minor allele was segregated in 54%. The present meta-analysis concluded that there is a segregation distortion favoring the expanded allele, among children of carriers. Therefore, further studies on transmissions and anticipation phenomena as well as more observations about fertility are required to clarify these selective forces over SCA3/MJD.
Collapse
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
| | - 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.,Instituto de Genética Médica Populacional, 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.,Instituto de Genética Médica Populacional, Porto Alegre, Brazil.,Departamento de Medicina Interna, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| |
Collapse
|
3
|
Genetic testing for clinically suspected spinocerebellar ataxias: report from a tertiary referral centre in India. J Genet 2018. [DOI: 10.1007/s12041-018-0911-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
4
|
Gan SR, Ni W, Dong Y, Wang N, Wu ZY. Population genetics and new insight into range of CAG repeats of spinocerebellar ataxia type 3 in the Han Chinese population. PLoS One 2015; 10:e0134405. [PMID: 26266536 PMCID: PMC4534407 DOI: 10.1371/journal.pone.0134405] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 07/08/2015] [Indexed: 12/21/2022] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3), also called Machado-Joseph disease (MJD), is one of the most common SCAs worldwide and caused by a CAG repeat expansion located in ATXN3 gene. Based on the CAG repeat numbers, alleles of ATXN3 can be divided into normal alleles (ANs), intermediate alleles (AIs) and expanded alleles (AEs). It was controversial whether the frequency of large normal alleles (large ANs) is related to the prevalence of SCA3 or not. And there were huge chaos in the comprehension of the specific numbers of the range of CAG repeats which is fundamental for genetic analysis of SCA3. To illustrate these issues, we made a novel CAG repeat ladder to detect CAG repeats of ATXN3 in 1003 unrelated Chinese normal individuals and studied haplotypes defined by three single nucleotide polymorphisms (SNPs) closed to ATXN3. We found that the number of CAG repeats ranged from 13 to 49, among them, 14 was the most common number. Positive skew, the highest frequency of large ANs and 4 AIs which had never been reported before were found. Also, AEs and large ANs shared the same haplotypes defined by the SNPs. Based on these data and other related studies, we presumed that de novo mutations of ATXN3 emerging from large ANs are at least one survival mechanisms of mutational ATXN3 and we can redefine the range of CAG repeats as: ANs≤44, 45 ≤AIs ≤49 and AEs≥50.
Collapse
Affiliation(s)
- Shi-Rui Gan
- Department of Neurology and Research center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China; Department of Neurology and Institute of Neurology, First Affiliated Hospital, Fujian Medical University, Fuzhou, China
| | - Wang Ni
- Department of Neurology and Research center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China
| | - Yi Dong
- Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Ning Wang
- Department of Neurology and Institute of Neurology, First Affiliated Hospital, Fujian Medical University, Fuzhou, China
| | - Zhi-Ying Wu
- Department of Neurology and Research center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China; Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| |
Collapse
|
5
|
Freund AA, Scola RH, Teive HAG, Arndt RC, da Costa-Ribeiro MCV, Alle LF, Werneck LC. Spinocerebellar ataxias: microsatellite and allele frequency in unaffected and affected individuals. ARQUIVOS DE NEURO-PSIQUIATRIA 2010; 67:1124-32. [PMID: 20069235 DOI: 10.1590/s0004-282x2009000600034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 08/14/2009] [Indexed: 02/05/2023]
Abstract
The diagnosis and incidence of spinocerebelar ataxias (SCA) is sometimes difficult to analyze due the overlap of phenotypes subtypes and are disorders of mutations caused by CAG trinucleotide repeat expansion. To investigate the incidence of the SCA in Southern Brazil, we analyzed the trinucleotide repeats (CAG)n at the SCA1, SCA2, SCA3, SCA6 and SCA7 loci to identify allele size ranges and frequencies. We examined blood sample from 154 asymptomatic blood donors and 115 individuals with progressive ataxias. PCR products were submitted to capillary electrophoresis. In the blood donors, the ranges of the five loci were: SCA1, 19 to 36 (CAG)n; SCA2, 6 to 28 (CAG)n; SCA3, 12 to 34 (CAG)n; SCA6, 2 to 13 (CAG)n; and SCA7, 2 to 10 (CAG)n. No deviations from Hardy-Weinberg equilibrium were detected. In the ataxia group, we found (CAG)n above the range of the asymptomatic blood donors in SCA3 (21.74%) followed by SCA2 (5.22%), SCA7 (2.61%), SCA6 (0.87%), and no cases of SCA1. The remaining 80 cases (69.56%) have different diagnoses from the type here studied. These data defined the alleles and their frequencies, as well as demonstrated their stability in the population not affected. The molecular diagnosis test confirmed the clinical diagnosis in 28/45 cases and classified another 7/70 from the clinical unclassified ataxias group.
Collapse
Affiliation(s)
- Aline Andrade Freund
- Neurology Division, Internal Medicine Department, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil
| | | | | | | | | | | | | |
Collapse
|
6
|
Gan SR, Shi SS, Wu JJ, Wang N, Zhao GX, Weng ST, Murong SX, Lu CZ, Wu ZY. High frequency of Machado-Joseph disease identified in southeastern Chinese kindreds with spinocerebellar ataxia. BMC MEDICAL GENETICS 2010; 11:47. [PMID: 20334689 PMCID: PMC2861663 DOI: 10.1186/1471-2350-11-47] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 03/25/2010] [Indexed: 12/23/2022]
Abstract
Background Machado-Joseph disease (MJD), caused by a CAG repeat expansion located in exon10 of the ATXN3 gene, is now regarded as one of the most common spinocerebellar ataxia (SCA) in the world. The relative frequency of MJD among SCA has previously been estimated at about 50% in the Chinese population and has been reported to be related to the frequency of large normal alleles in some populations. Taq polymerase has been used for PCR in nearly all studies reported previously. Methods Normal and expanded alleles of ATXN3 were detected via PCR using LA Taq DNA polymerase (better for GC-rich sequences) and denaturing polyacrylamide gel electrophoresis in 150 normal individuals and 138 unrelated probands from autosomal dominant SCA families. To compare reaction efficiency, 12 MJD patients' expanded alleles were amplified with La Taq and Taq polymerase respectively in the same amplifying systems and reaction conditions. Results Normal alleles ranged from 12 to 42 CAG repeats. The most common allele contained 14 repeats with a frequency of 23.3%, which corroborates previous reports. The frequency of large normal alleles (>27 repeats) was 0.28, which was very high relative to previous reports. The frequency of MJD in SCA patients was 72.5%, which was significantly higher than those in previous reports about the Chinese and other Asian populations. This frequency was one of the highest reported worldwide, with only Portuguese and Brazilian populations exhibiting higher proportions. All 12 expanded alleles were amplified in PCR with La Taq polymerase, whereas only 2 expanded alleles were amplified with Taq polymerase. Conclusion We have first reported the highest relative frequency of MJD in Asia, and we attribute this high frequency to a more efficient PCR using LA Taq polymerase and hypothesized that large ANs may act as a reservoir for expanded alleles in the Southeastern Chinese population.
Collapse
Affiliation(s)
- Shi-Rui Gan
- Department of Neurology and Institute of Neurology, Huashan Hospital, State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, 12 Wulumuqi Zhong Road, Shanghai 200040, China
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Martins S, Calafell F, Wong VCN, Sequeiros J, Amorim A. A multistep mutation mechanism drives the evolution of the CAG repeat at MJD/SCA3 locus. Eur J Hum Genet 2006; 14:932-40. [PMID: 16724006 DOI: 10.1038/sj.ejhg.5201643] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Despite the intense debate around the repeat instability reported on the large group of neurological disorders caused by trinucleotide repeat expansions, little is known about the mutation process underlying alleles in the normal range that, ultimately, expand to pathological size. In this study, we assessed the mutation mechanisms by which wild-type Machado-Joseph disease (MJD) alleles have been generated throughout human evolution. Haplotypes including the CAG repeat, six intragenic SNPs and four flanking microsatellites were analysed in 431 normal chromosomes of European, Asian and African origin. A bimodal CAG repeat length frequency distribution was found in the four most frequent wild-type lineages (H1-GCGGCA; H2-GTGGCA; H3-TTAGAC and H4-TTACAC). Based on flanking microsatellite haplotypes, the variance calculated by analysis of molecular variance between modal (CAG)n alleles was little or null in lineages H1, H2 and H4, as were the pairwise differences. Moreover, genetic distances among all the alleles from each lineage did not reflect the allele sizes differences, as expected if a stepwise mutation model was the main process of evolution. On the contrary, when exposed in maximum parsimonious phylogenetic trees, a large number of mutation steps separated same-size alleles, whereas several microsatellite haplotypes were shared by modal CAGs. In conclusion, our results suggest that the main mutation mechanism occurring in the evolution of the polymorphic CAG region at MJD/SCA3 locus is a multistep one, either by gene conversion or DNA slippage; repeats with 14, 21, 23 and 27 CAGs are the main alleles involved in this process.
Collapse
Affiliation(s)
- Sandra Martins
- IPATIMUP - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal.
| | | | | | | | | |
Collapse
|
8
|
Bauer PO, Zumrova A, Matoska V, Marikova T, Krilova S, Boday A, Singh B, Goetz P. Absence of spinocerebellar ataxia type 3/Machado-Joseph disease within ataxic patients in the Czech population. Eur J Neurol 2005; 12:851-7. [PMID: 16241973 DOI: 10.1111/j.1468-1331.2005.01090.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although spinocerebellar ataxia type 3 (SCA3)/Machado-Joseph disease is the most common type of SCA worldwide, we did not identify any cases of the disease amongst SCA patients in the Czech population. It has been proposed that the prevalence of large normal alleles correlates with the frequency of various types of SCA. We have therefore attempted to resolve the absence of SCA3 in our population by investigating, within 204 normal chromosomes, the frequency and nature of CAG repeats as well as two intragenic polymorphisms. We found that large normal alleles with more than 33 CAG repeats were observed at a frequency of only 0.49%. Whereas most of the expanded alleles worldwide have the CA haplotype, this was the least common (5.4%) variant observed in our study, although it was associated with a larger mean CAG repeat length (26.9). We postulate that the absence of SCA3 in the Czech population might be explained by the lack of large normal alleles and consequently a relatively small reservoir for aberrant CAG expansions at the SCA3 locus.
Collapse
Affiliation(s)
- P O Bauer
- Neurogenetic Centre of the Institute of Biology and Medical Genetics, Department of Child Neurology, 2nd Medical Faculty of Charles University and Faculty Hospital Motol, Prague, Czech Republic.
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Chattopadhyay B, Gupta S, Gangopadhyay PK, Das SK, Roy T, Mukherjee SC, Sinha KK, Singhal BS, Bhattacharyya NP. Molecular analysis of GAA repeats and four linked bi-allelic markers in and around the frataxin gene in patients and normal populations from India. Ann Hum Genet 2004; 68:189-95. [PMID: 15180699 DOI: 10.1046/j.1529-8817.2003.00087.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Friedreich ataxia (FRDA), the most common type of ataxia worldwide, is an autosomal recessive disease. Homozygous expansion of GAA repeats in the first intron of the frataxin gene constitute the major type of mutation that causes the disease. The prevalence of FRDA in diverse ethnic populations of India has not been widely studied. We have studied the distribution of polymorphic GAA repeats in the frataxin gene among 6 clinically diagnosed patients and 160 ethnically matched normal individuals, to gather information on the prevalence of FRDA in the eastern part of India. Homozygous expansion in the range of 250-730 GAA repeats was detected among the patients. Among normal individuals, we observed a unimodal distribution of GAA repeats, consisting of 10 different alleles ranging from 7 to 16 GAA repeats, where the 9 repeat allele had maximal frequency. Only 5.9% of all chromosomes were found to harbour >12 GAA repeats. Haplotype analysis using closely linked four bi-allelic markers in and around the frataxin gene indicated that 66.7% of the expanded alleles harbour the ATCC haplotype that has been reported worldwide. This haplotype was present in 53.3% of the chromosomes with >12 GAA repeats, and accounted for only 3.8% of chromosomes with 7 to 12 GAA repeats. We found one novel haplotype, ACCT, among the expanded alleles as well as among normal individuals, though at low frequency; this haplotype may be characteristic of Indian populations.
Collapse
Affiliation(s)
- B Chattopadhyay
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata: 700 064, India
| | | | | | | | | | | | | | | | | |
Collapse
|