ATXN1 and autosomal dominant cerebellar ataxia: While the C9orf72 STR expansion is the most established genetic basis for ALS and FTD, intermediate STR expansions within the Spinocerebellar ataxia (SCA) genes ATXN1 (SCA1) and ATXN2 (SCA2) have emerged as noteworthy contributors to ALS susceptibility [3].