LRRK2 and Parkinson disease: Although multiple genes have been shown causative for PD (Table 1), two important PD causative genes identified so far are SNCA and LRRK2. SNCA encodes α-synuclein, a major component of pathological hallmark of Lewy bodies in PD,13 while mutations in LRRK2 are the most common indicators of inherited PD.14