Spinocerebellar ataxia type 1 (SCA1), spinocerebellar ataxia type 2 (SCA2) and Huntington disease are autosomal-dominant genetically determined neurodegenerative diseases, caused by the expanded CAG repeats (polyglutamine, polyQ) at the ATXN1, ATXN2 and HTT genes, respectively. This evidence concerns the gene ATXN2 and spinocerebellar ataxia type 2.