SNCA and Parkinson disease: SNCA was the first gene to be associated to familial cases of PD (Polymeropoulos et al., 1997) and it encodes alpha-synuclein (α-syn), a small 14 kDa protein that was also found to accumulate in the Lewy bodies, the proteinaceous structures that mark the histopathology of PD (Spillantini et al., 1998).