SNCA and Parkinson disease: The identification of point mutations in the SNCA gene in familial cases of PD nearly 23 years ago first linked α-syn to PD [62], and this was corroborated by the additional discovery that increased genetic copies of α-synuclein in the form of duplications and triplications of the SNCA gene are enough to cause PD; the higher gene copy, the earlier the age of disease onset and the more severe the disease [63,64,65].