SNCA and Parkinson disease: Genetic-based models of PD and parkinsonism have involved familial PD-associated mutant forms of SNCA (A53T, A30P, E46K), overexpression or knock-in mutations of LRRK2 (G2019S, R1441C/G), or deletion or knock-out of PRKN, PINK1, and/or DJ-1.