title: Analysis of CAG repeats in SCA1, SCA2, SCA3, SCA6, SCA7 and DRPLA loci in spinocerebellar ataxia patients and distribution of CAG repeats at the SCA1, SCA2 and SCA6 loci in nine ethnic populations of eastern India.
abstract: To identify various subtypes of spinocerebellar ataxias (SCAs) among 57 unrelated individuals clinically diagnosed as ataxia patients we analysed the SCA1, SCA2, SCA3, SCA6, SCA7 and DRPLA loci for expansion of CAG repeats. We detected CAG repeat expansion in 6 patients (10.5%) at the SCA1 locus. Ten of the 57 patients (17.5%) had CAG repeat expansion at the SCA2 locus, while four had CAG expansion at the SCA3/MJD locus (7%). At the SCA6 locus there was a single patient (1.8%) with 21 CAG repeats. We have not detected any patient with expansion in the SCA7 and DRPLA loci. To test whether the frequencies of the large normal alleles in SCA1, SCA2 and SCA6 loci can reflect some light on prevalence of the subtypes of SCAs we studied the CAG repeat variation in these loci in nine ethnic sub-populations of eastern India from which the patients originated. We report here that the frequency of large normal alleles (>31 CAG repeats) in SCA1 locus to be 0.211 of 394 chromosomes studied. We also report that the frequency of large normal alleles (>22 CAG repeats) at the SCA2 locus is 0.038 while at the SCA6 locus frequency of large normal alleles (>13 repeats) is 0.032. We discussed our data in light of the distribution of normal alleles and prevalence of SCAs in the Japanese and white populations.
authors.affiliation: Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Bidhan Nagar, Calcutta, India.
authors.forename: P
authors.initials: P
authors.lastname: Basu
authors.forename: B
authors.initials: B
authors.lastname: Chattopadhyay
authors.forename: P K
authors.initials: PK
authors.lastname: Gangopadhaya
authors.forename: S C
authors.initials: SC
authors.lastname: Mukherjee
authors.forename: K K
authors.initials: KK
authors.lastname: Sinha
authors.forename: S K
authors.initials: SK
authors.lastname: Das
authors.forename: S
authors.initials: S
authors.lastname: Roychoudhury
authors.forename: P P
authors.initials: PP
authors.lastname: Majumder
authors.forename: N P
authors.initials: NP
authors.lastname: Bhattacharyya
mesh_terms: D000293:Adolescent; D000328:Adult; D000483:Alleles; D000067696:Ataxin-1; D000067699:Ataxin-3; D000067719:Ataxin-7; D000067528:Ataxins; D015220:Calcium Channels / Q000235:genetics; D002648:Child; D005006:Ethnicity / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D006580:Genetic Carrier Screening; D005820:Genetic Testing; D006801:Humans; D007194:India / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics; D011506:Proteins / Q000235:genetics; D012097:Repressor Proteins; D020754:Spinocerebellar Ataxias / Q000175:diagnosis / Q000208:ethnology* / Q000235:genetics*; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D018911:Trinucleotide Repeats / Q000235:genetics*; D044465:White People / Q000235:genetics*; D020864:Calcium Channels, N-Type
chemical_list: D000067696:Ataxin-1; D000067699:Ataxin-3; D000067719:Ataxin-7; D000067528:Ataxins; D015220:Calcium Channels; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011506:Proteins; D012097:Repressor Proteins; C000593749:ATXN1 protein, human; C000593829:ATXN7 protein, human; C105656:CACNA1A protein, human; D020864:Calcium Channels, N-Type; C095278:atrophin-1; C092341:ATXN3 protein, human