Many studies have suggested that alterations in the levels of specific neurotrophic factors (NTFs), such as brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), are associated with the pathogenesis of neurodegenerative diseases such as AD and Parkinson’s disease (PD) [3,5,6,7,8,9,10,11]. The gene discussed is BDNF; the disease is Parkinson disease.