DRD2 and Huntington disease: Remarkably, down-regulated genes display a neuronal signature, since decreased genes in HD striatum are enriched in genes that define striatal neuron identity and function, such as Darpp32, Rgs9, Drd1 or Drd2 (Hodges et al., 2006; Kuhn et al., 2007; Vashishtha et al., 2013; Achour et al., 2015; Langfelder et al., 2016).