The main pathological hallmark of PD is the progressive death of dopaminergic neurons in the substantia nigra (SN) and deposition of Lewy bodies (LBs), fibrillar aggregates composed of α-synuclein (α-syn), leucine-rich repeat kinase 2 (LRRK2), and other proteins (Lang and Lozano, 1998; Wakabayashi et al., 2013). The gene discussed is LRRK2; the disease is Parkinson disease.