Several lines of evidence demonstrate the pathogenic role of α-Syn in PD: 1) point mutations (A30P, E46K, H50Q, G51D, A53T, and A53E) and duplication or triplication of the SNCA gene cause autosomal dominant forms of PD (Polymeropoulos et al., 1997; Zarranz et al., 2004); 2) polymorphic variants of the SNCA gene constitute an important risk factor for developing idiopathic PD (Nalls et al., 2014); and 3) α-Syn is the major component of Lewy bodies (Spillantini et al., 1997; Wakabayashi et al., 2013). This evidence concerns the gene SNCA and Parkinson disease.