ATXN1 and spinocerebellar ataxia type 1: Expansion of the CAG repeats above 44 in the ATXN1 gene causes spinocerebellar ataxia type 1 (SCA1), while more than 35 CAG repeats in the ATXN2 gene is the cause of spinocerebellar ataxia type 2 (SCA2) [48].