Preclinical studies investigating the role of α-synuclein in PD utilized overexpression of α-synuclein [45] or more recently seeding of α-synuclein misfolding and aggregation with prion-like preformed α-synuclein fibrils (PFFs) [46] both in vitro and in animal models [16, 46]. The gene discussed is SNCA; the disease is Parkinson disease.