LRRK2 and Parkinson disease: Mutations in three proteins encoded by these genes, namely, parkin (PARK2), DJ-1 (PARK7), and PINK1 (PARK6), are associated with recessive early onset forms of PD, whereas mutations in α-synuclein (PARK1–4) and LRRK2 (PARK8) are responsible for dominant forms of familial PD.