Spinocerebellar ataxias: microsatellite and allele frequency in unaffected and affected individuals.
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.
Freund
Aline Andrade
AA
Neurology Division, Internal Medicine Department, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Scola
Rosana Hermínia
RH
Teive
Hélio A G
HA
Arndt
Raquel Cristina
RC
da Costa-Ribeiro
Magda Clara Vieira
MC
Alle
Lupe Furtado
LF
Werneck
Lineu Cesar
LC
D000328:Adult; D001938:Brazil; D016022:Case-Control Studies; D019075:Electrophoresis, Capillary; D005260:Female; D005787:Gene Frequency / Q000235:genetics*; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics*; D020754:Spinocerebellar Ataxias / Q000175:diagnosis / Q000235:genetics*; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*
D011506:Proteins