Aberrant polyglutamine expansion within the human ATXN2 gene causes spinocerebellar ataxia type 2 (SCA2) and is strongly linked to ALS as well as the atypical parkinsonian disorder called progressive supranuclear palsy (PSP; Pulst et al., 1996; Elden et al., 2010; Ross et al., 2011). This evidence concerns the gene ATXN2 and amyotrophic lateral sclerosis.