Brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), and nerve growth factor (NGF) are three important neurotrophins involved in neurogenesis and pathophysiology of many nervous system diseases (Angelucci et al. 2004, Allen et al. 2013, de Azevedo Cardoso et al. 2014, Castren & Monteggia 2021). The gene discussed is GDNF; the disease is nervous system disorder.