NTRK2 and obesity due to melanocortin 4 receptor deficiency: Hypomorphic expression of the TrkB.FL causes hyperphagia-induced obesity due to reduced hypothalamic BDNF signaling, while genetic deletion of TrkB.T1 leads to increased anxiety related behavior associated with structural alterations in neurites of the amygdala (Carim-Todd et al., 2009; Xu et al., 2003).