For example, nerve growth factors (NGF, encoded by NGF gene), which are reported to be involved in many physiological functions, including memory enhancement, death prevention, and functional state stimulation of cholinergic neurons, are used as a prototype of the neurotrophin in AD treatment.[69] Though functional variants and the biological pathways remain to be further investigated for most of the AD loci, various gene therapy studies have been carried out to target the AD‐implicating genes as detailed in Section 3. The gene discussed is BDNF; the disease is Alzheimer disease.