LRRK2 and Parkinson disease: Currently, over 20 causative or putative genes of hereditary PD have been identified by genetic linkage analysis [20]; for example, SNCA (PARK1, PARK4), Parkin (PARK2), DJ-1 (PARK7), and LRRK2 (PARK8) [21,22,23,24,25,26,27], which encode α-synuclein, Parkin, protein/nucleic acid deglycase DJ-1, and leucine-rich repeat kinase 2 (LRRK2) protein, respectively.