Further understanding of the mechanism of BDNF-TrkB or BDNF-TrkB.T1 signaling, and their regulatory functions in the survival and maintenance of DAergic neurons, will provide a novel and practical approach to study the pathology of neurodegenerative diseases like AD, PD, and Huntington’s disease, and investigate potential therapeutic strategies. The gene discussed is NTRK2; the disease is Alzheimer disease.