α-Synuclein (α-syn) protein is implicated in the etiology of PD, not only because mutations and duplications/triplications in SNCA, the gene encoding α-syn, cause early onset familial PD, but also because the protein itself is a principle component of intraneuronal aggregations called Lewy bodies, the histopathological hallmark of PD [30]. Here, SNCA is linked to Parkinson disease.