The first observations of the neuroprotective properties of GDNF in animal models of PD started to be documented 1 year after the original Lin, and Collins GDNF study (Hoffer et al., 1994; Beck et al., 1995; Tomac et al., 1995), and the first report of positive effects in nonhuman primate models of PD was published 1 year later, and rigorous studies followed afterward (Bowenkamp et al., 1995; Gash et al., 1995, 1996, 2005; Sauer et al., 1995; Zhang et al., 1997; Rosenblad et al., 2000; Ai et al., 2003). The gene discussed is GDNF; the disease is Parkinson disease.