SNCA and Parkinson disease: Although genetic forms of PD associated with mutations in genes for alpha-synuclein, PARKIN, PINK1, LRRK2 or DJ-1 are well established (reviewed in Henchcliffe and Beal 2008), increasing evidence suggests a role for gene–environmental interactions contributing to the sporadic form of the disease, and gene regulatory networks are being unraveled (Kumar Singh et al. 2014; Krug et al. 2014; Fujita et al. 2014; Todorovic et al. 2014; Maertens et al. 2015; Lee and Cannon 2015; Rahnenführer and Leist 2015).