For example, ATXN2 encodes a polyglutamine protein associated with spinocerebellar ataxia 2 (Imbert et al., 1996) and contains an expansion that also confers increased susceptibility to ALS in sporadic (Elden et al., 2010), and possibly C9 (van Blitterswijk et al., 2014), cases. Here, C9 is linked to amyotrophic lateral sclerosis.