SNCA and Parkinson disease: Pathogenic missense mutations (A53T [16], A30P [17], E46K [18] and H50Q [19] and G51D [20] [PARK1] which leads to misfolding and promotes apoptosis) and changes in gene dosage (duplications, triplications [PARK4] which leads to an excess and aggregation of α-syn) are associated with PD (Fig. 2).