Comparative transcriptomics of lateral hypothalamic cell types reveals conserved growth hormone-tachykinin dynamics...

The lateral hypothalamus (LH) plays a central role in appetite control, however the functional and evolutionary conservation of its subcircuits remain unclear. This study aimed to define the molecular and cellular identities of zebrafish LH neurons, identify conserved LH cell types across vertebrates, and investigate their roles in appetite regulation.

We performed the Act-seq method of single-cell RNA sequencing in the larval zebrafish LH under food-deprived and voracious feeding states to capture activity-dependent transcriptional signatures. Using integrative comparative transcriptomics, we aligned zebrafish neuronal clusters with a published mouse LH dataset to identify conserved neuronal sub-populations, and performed functional and molecular characterisation of a highly-conserved cell type in both zebrafish and mice.

We identified several LH neuronal subtypes in zebrafish that are differentially activated during voracious feeding. Cross-species mapping revealed overlapping cellular clusters, especially for GABAergic neurons. We report a conserved GABAergic cluster co-expressing growth hormone (GH) receptors and tachykinin. In both species, feeding activates these neurons and elevates GH receptor and tachykinin expression. In zebrafish, upstream GH signaling is similarly regulated by feeding state, and acute GH administration both activates this cluster and enhances food intake.

These findings uncover a conserved GH receptor-tachykinin LH population which may link metabolic hormone signaling to appetite control. Beyond its established long-term roles in growth and metabolism, we propose that GH exerts acute appetite-enhancing effects through activation of this neuronal pathway. Our comparative LH atlas highlights the evolutionary biology of hypothalamic appetite circuits.