DRD1 and Huntington disease: Among the genes with aberrant expression in HD striatum are transcriptional regulators (e.g., Fos, Egr1, Npas4, and Polr2a) as well as key neuronal genes important for neurotransmitter signaling (e.g., Drd1, Drd2, Grin3a, and Ppp1r1b) and synaptic plasticity (e.g., Arc and Syp) (Seredenina and Luthi-Carter, 2012; Vashishtha et al., 2013; Yildirim et al., 2019).