SNCA and Parkinson disease: Alpha-synuclein is the major protein component of Lewy bodies and Lewy neurites in PD brain (Spillantini et al., 1997) and both point mutations and multiplications of the alpha-synuclein gene, as well as polymorphisms that increase expression, have been associated with familial PD (Fuchs et al., 2007; Ross et al., 2008).