Specifically, Mendelian forms of PD have been of particular interest including SNCA, which is the focus of this review, leucine-rich repeat kinase 2 (LRRK2), glucosidase, beta, acid (GBA), PTEN-induced putative kinase 1 (PINK1), or PARKIN (reviewed in Hartfield et al., 2012; Torrent et al., 2015). Here, PINK1 is linked to Parkinson disease.