These critical findings established the importance of ATXN2 as a common contributor to ALS and provided yet another example of proteins misfolding across multiple neurodegenerative disorders, as ATXN2 can also contribute to Parkinson’s disease and mutations in ATXN2 cause SCA2 (Imbert et al., 1996; Pulst et al., 1996; Sanpei et al., 1996; Lorenzetti et al., 1997; Infante et al., 2004; Nanetti et al., 2009; Fischbeck and Pulst, 2011). Here, ATXN2 is linked to Parkinson disease.