Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative dis-ease caused by the expansion of cytosine–adenine–guanine (CAG) repeats in the ataxin-1 (ATXN1) gene, leading to toxic gain-of-function of the ataxin-1 (ATXN1) protein. This evidence concerns the gene ATXN1 and spinocerebellar ataxia type 1.