Identification of PD-linked mutations in the α-synuclein encoding SNCA gene [2, 10, 48, 56] has led to the development of α-synuclein transgenic and viral overexpression animal models to study both the normal function of α-synuclein and the mechanisms by which α-synuclein aggregation causes neurodegeneration. The gene discussed is SNCA; the disease is Parkinson disease.