RGS6 and bipolar disorder: Finally, by integrating MSN subtype-specific transcriptomes and ATAC-seq-derived regulatory annotations with human GWAS data, we demonstrate strong, cell-type-specific enrichment of polygenic risk for Parkinson’s disease, substance use disorders, and psychiatric and cognitive traits, including a striking association of D2-VS-RGS6 with schizophrenia and bipolar disorder.