Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic protein for dopaminergic and other neurones (Lin et al., 1993; Airaksinen and Saarma, 2002) and shows robust neurorestorative and neuroprotective effects in nonhuman primate models of Parkinson’s disease when administered to targets within the CNS (Gash et al., 1996; Zhang et al., 1997; Grondin et al., 2002; Allen et al., 2013). The gene discussed is GDNF; the disease is Parkinson disease.