LRRK2 and Parkinson disease: In the present study we have systematically investigated RAC1 function in three disease models of PD including the following: (a) C elegans models of PD; (b) human-derived neuroblastoma BE(2) (M17) cells stably over-expressing α-SYN, wherein amyloidigenic accumulation of α-SYN is induced by sodium butyrate; and (c) iPSC-derived DAn generated by cell reprogramming of somatic skin cells from patients with monogenic LRRK2-associated PD [20].