DRD1 and Huntington disease: Importantly, physiological age-dependent transcriptional changes of neuronal- and glial-specific genes were accelerated by the HD mutation: neuronal-specific genes, most particularly genes specific to MSN expressing D1 dopamine receptor (D1 MSN), including Drd1, were lower in Q140 than in WT striata at both ages, whereas glial-specific genes (e.g. Tmem151b20), were increased in Q140 vs WT striatum (Fig. 3b and Supplementary Fig. 11a, b).