Linkage disequilibrium at the SCA2 locus

摘要: Spinocerebellar ataxia type 2 (SCA2) is caused by the expansion of an unstable CAG repeat encoding a polyglutamine tract. Repeats with 32 to 200 CAGs are associated disease, whereas normal chromosomes contain 13 33 repeats. We tested 220 families different geographical origins for SCA2 mutation. Thirty three were positive (15%). Twenty at least two affected subjects linkage disequilibium (LD) between mutation and microsatellite markers, which (D12S1332-D12S1333) closely flanked mutation; other (D12S1672) was intragenic. Many haplotypes observed, indicating occurrence several ancestral mutations. However, same haplotype, not observed in controls, detected German, Serbian, some French families, suggesting founder effect or recurrent mutations on risk haplotype.