The α-synuclein is a major component of Lewy bodies that may bind to TH and inhibit its activity, while loss of TH activity and reduced protein levels are thought to be responsible for decreased DA levels and the PD phenotype (Nagatsu, 1990; Blanchard-Fillion et al., 2001; Perez et al., 2002; Corti et al., 2011). The gene discussed is TH; the disease is Parkinson disease.