SNCA and familial disease: This is evidenced by the finding that various point mutations in the gene encoding α-synuclein, SNCA (such as A53T), cause early-onset familial disease (Appel-Cresswell et al., 2013; Krüger et al., 1998; Lesage et al., 2013; Polymeropoulos et al., 1997; Proukakis et al., 2013; Zarranz et al., 2004), as do gene duplications (Chartier-Harlin et al., 2004) and triplications (Singleton et al., 2003).