Studies on human HD tissue samples and YAC72, BACHD and R6/2 mice (Zuccato et al., 2001, 2005, 2008; Gray et al., 2008) show that cortical BDNF mRNA expression is impaired, suggesting this reduces BDNF supply to the striatum in these HD models. The gene discussed is BDNF; the disease is Huntington disease.