ATXN2 and spinocerebellar ataxia type 2: Ataxin-2 is a polyglutamine (polyQ) protein in which long (>34) polyQ expansions cause spinocerebellar ataxia 2 (SCA2) (Imbert et al., 1996; Pulst et al., 1996; Sanpei et al., 1996), and intermediate-length (27–33) repeats are a risk factor for ALS (Elden et al., 2010).