Spinocerebellar ataxia type 6: founder effect in Western Japan.

An accumulation of SCA6 cases has been observed in the Chugoku area of Western Japan. In the Tottori prefecture, located in the northeastern part of the Chugoku district, we observed a cluster of SCA6 families within the eastern area, suggesting that there may be a founder in the Japanese SCA6 population. Genotyping with DNA microsatellite markers linked to the CACNL1A4 gene on chromosome 19p13 demonstrated shared allelic characteristics and revealed a common haplotype in the majority of Japanese families. The common haplotype of the shared (CAG)(22) repeat found in this study may indicate the meiotic stability of CAG repeats in SCA6 patients.