ATXN2 and amyotrophic lateral sclerosis: In terms of the present review, the most interesting protein is ATXN2, as the expanded repeat tract in ATXN2 is responsible for spinocerebellar ataxia type 2 (SCA2) [81], as well as normal ATXN2 is implicated in amyotrophic lateral sclerosis (ALS) [82].