The potency of neurotrophic factors, particularly NGF, BDNF, CNTF and GDNF, in promoting neuronal survival has raised much hope for their therapeutic use in neurodegenerative diseases including Alzheimer’s disease, Huntington’s disease, amyotrophic lateral sclerosis (ALS), Parkinson’s disease and glaucoma [2,3,4]. The gene discussed is GDNF; the disease is Parkinson disease.