[Molecular analyses of intergenerational instability of CAG repeat in SCA2 gene].

Spinocerebellar Ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder caused by unstable expansion of a CAG repeat, and the intergenerational change in the number of CAG repeat units has been shown to result in genetic anticipation of SCA2. To elucidate the molecular mechanism of intergenerational instability of CAG repeat, 16 affected parent-affected offspring pairs were studied. The mean intergenerational changes of CAG repeat were 5.3 +/- 6.9 repeat in paternal transmission (n = 11) and 2.8 +/- 3.1 repeat in maternal transmission (n = 5). Two CAA insertion pattern (CAG)8CAA(CAG)4CAA(CAG)8 and (CAG)13CAA(CAG)8 were found in normal alleles, and there was no significant correlation CAA insertion pattern of parents normal allele and the intergenerational change of CAG repeat.