In line with this notion, increased TH expression has been observed in discrete areas of the VTA in individuals with PD (Tong et al., 2000), and studies in MPTP non-human primate models have demonstrated that increased striatal TH expression peaks before the manifestation of motor symptoms in PD (Bubak et al., 2015; Tandé et al., 2006). The gene discussed is TH; the disease is Parkinson disease.