In HD, BDNF and the BDNF receptors (TrkB) are substantially reduced as a consequence of epigenetic and transcriptional regulation (Zuccato et al., 2008), and BDNF-TrkB signaling is thought to be a major contributor to the progressive neuronal degeneration (Ginés et al., 2006). The gene discussed is NTRK2; the disease is Huntington disease.