LRRK2 and Parkinson disease: DA is also involved in the PD pathogenesis associated with genetic factors, including SNCA (encoding α-synuclein [α-syn]), LRRK2 (leucine-rich repeat kinase 2), PINK1 (PTEN-induced kinase 1), Parkin, DJ-1 and GBA1 (glucocerebrosidase-1 [GCase]), contributing to DA neuronal degeneration [15–19].