LRRK2 and Parkinson disease: Although the low incidence of sporadic PD is extremely low, recent studies found that many of the genes in familial PD plays an essential role in mitochondrial function, such as α-synuclein (PARK1), UCHL1 (PARK5), LRRK2 (PARK8) dominant mutation, PINK1 (PARK6), DJ-1 (PARK7) mutations, and Parkin (PARK2) [7].