Single-cell sequencing of rodent ventral pallidum reveals diverse neuronal subtypes with non-canonical interregional continuity

Abstract

The ventral pallidum (VP) was defined as a basal ganglia nucleus with dense input from ventral striatum. To further investigate a VP regional identity, we conducted a cross-species transcriptional characterization of VP cell types. We performed single nucleus RNA-sequencing of VP tissue from mice and rats and identified 16 VP neuronal subclasses with striking cross-species conservation. VP GABAergic neurons were surprisingly heterogeneous, consisting of 14 sub-classes from 3 developmental classes. Combining our sequencing data with a spatial atlas revealed that all VP subclasses extended beyond the traditional borders of VP. Integrating our VP data with prior sequencing data from striatal, hypothalamic, and extended amygdalar tissue confirmed that cell types are shared among these regions. Due to the role of VP in feeding behavior, we also assessed the transcriptional impact of high-fat diet consumption, which induced altered expression of genes involved in oxidative phosphorylation and inhibitory signaling. Overall, our results demonstrate that VP is not a transcriptionally discrete nucleus; rather, VP contains cell types with diverse expression patterns that overlap with regions beyond the basal ganglia.

Transcriptomic landscape of mammalian ventral pallidum at single-cell resolution

“…We identified 16 clusters of GABAergic neurons in the mouse VP, many of which corresponded to the GABAergic neurons previously described in basal forebrain structures ( 26 , 28 , 29 ). GABAergic neuronal clusters were differentiated based on enrichment of genes encoding neuropeptides (i.e.…”

“…These cell types exhibit distinct transcriptional profiles and are marked by high expression levels of canonical marker genes of each type (Fig. 1C, Table S2; 26 , 27 ).…”

“…Our results corroborate this interpretation at the transcriptional level. Specifically, we identified VP populations in mice that share marker genes for accumbal medium sized spiny neurons ( PDZD2 colocalized with either the DRD1 or DRD2 ( 30 , 31 , 64 ), clusters with transcriptional homologues in the extended amygdala (SLC17A7_CCK, DNAH5_VIPR2; 28 , 65 , 66 ) and glutamatergic neurons with transcriptional homology to those expressed in BNST (SLC17A6_MASP1; 26 , 30 , 31 ). Recent reports have corroborated this interpretation, finding that transcriptionally defined cell types are expressed in multiple forebrain structures that share borders with the VP (26, 33, 34).…”

“…Specifically, we identified VP populations in mice that share marker genes for accumbal medium sized spiny neurons ( PDZD2 colocalized with either the DRD1 or DRD2 ( 30 , 31 , 64 ), clusters with transcriptional homologues in the extended amygdala (SLC17A7_CCK, DNAH5_VIPR2; 28 , 65 , 66 ) and glutamatergic neurons with transcriptional homology to those expressed in BNST (SLC17A6_MASP1; 26 , 30 , 31 ). Recent reports have corroborated this interpretation, finding that transcriptionally defined cell types are expressed in multiple forebrain structures that share borders with the VP (26, 33, 34). However, it is critical to note that while AIBS MERFISH data was generated using a 500-gene panel covering unique sets of marker genes across the brain, these marker genes are not fine-tuned to label molecularly defined transcriptomic clusters unique to several brain regions.…”

“…These cell types exhibit distinct transcriptional profiles and are marked by high expression levels of canonical marker genes of each type (Fig. 1C, Table S2; (26,27). Among all transcriptional cell types, neurons exhibited a high degree of transcriptional heterogeneity based on inspection of the UMAP (Fig.…”