ATXN2 and cerebellar ataxia: For instance, non-pathogenic alleles of the spinocerebellar ataxia-related genes ATXN1 (SCA1; OMIM 164400) and ATXN2 (SCA2; OMIM 183090) have tracts interrupted by 1–3 CAT (His) codons in ATXN1 and CAA (Gln) codons in ATXN2 [13,14,15].