Altered levels of BDNF, both in the circulating blood and in the CNS tissues, have been reported to be involved in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD), and multiple sclerosis (MS) as well as in ischemic stroke [5–10]. The gene discussed is BDNF; the disease is Parkinson disease.