SNCA and Parkinson disease: This evidence, together with the identification of mutations in the gene that encodes for this protein (SNCA) as the cause behind familial cases of PD (Polymeropoulos et al., 1997) and the observation that duplications and triplications of the SNCA gene lead to highly penetrant forms of the disease (Singleton et al., 2003; Ibanez et al., 2004) directly connect PD and α-Syn.