Transcriptomic profiling of hypothalamic feeding networks reveals neuropeptide diversity, conserved gene expression, and feeding state dependent regulation

The lateral and ventromedial hypothalamus are commonly referred to as the hunger and satiety centers in mammals. We previously identified two hypothalamic loci in zebrafish, the lateral and caudal hypothalamus, that are bidirectionally active across hunger, voracious feeding, and satiety states, and which contribute towards the homeostatic control of feeding (Wee et al, eLife, 2019). However, the precise cellular identities of these circuits, as well as potential mechanisms of interactions between them were still unknown. Using zebrafish, we first conducted bulk transcriptomic profiling of these loci. In both regions, we identified conserved expression of several neuropeptides and receptors with known functions in appetite regulation. We also found neuromodulator-receptor pairs across the two hypothalamic loci which support potential crosstalk mechanisms. Using in situ hybridisation chain reaction, we analyzed the activity and expression patterns of prominent neuropeptides such as tachykinin 1 (tac1), prodynorphin (pdyn), and somatostatin 1 (sst1). In starved, voraciously feeding and satiated fish, and observed dynamic changes in neuropeptide expression and activity patterns across hunger and satiety states. Finally, the ACT-seq method of single-cell RNA sequencing was used to further categorize and characterize the cell types activated during voracious feeding, which corresponded to spatially segregated hypothalamic cluster. Notably, a tac1 and ghra-positive cluster in the lateral hypothalamus was confirmed to be highly active during voracious feeding. Overall, this new data has advanced our understanding of how interacting hypothalamic loci regulate energy balance in the vertebrate brain. If time permits, I will also share how we are now linking these hypothalamic circuits to diet-microbiome interactions and their effects on feeding behavior.