A spatial and projection-based transcriptomic atlas of paraventricular hypothalamic cell types.

The paraventricular hypothalamus (PVH) controls many behavioral and physiologic processes, including appetite, social behavior, autonomic outflow, and pituitary hormone secretion. However, molecular markers for centrally-projecting PVH neuron populations remain largely undefined, and a complete census of PVH cell types has not been established. Therefore, we performed extensive single-cell/nucleus RNA sequencing to catalog PVH neuron subtypes and multiplexed error-robust fluorescence in situ hybridization (MERFISH) to map them spatially. Our spatial transcriptomic atlas resolves 26 Sim1+ and 29 GABAergic neuron populations from the PVH and surrounding areas, revealing multiple subtypes not described previously and distinct transcriptional programs between neuroendocrine and centrally-projecting neurons. Additionally, projection-based profiling determined neuronal subtypes that project to the parabrachial region (PB) and spinal cord, helping to identify PVH populations that regulate satiety and sympathetic nervous system activity, respectively. Notably, activation of PB-projecting PVH neurons expressing bombesin-like receptor 3 (Brs3) reduces food intake and silencing them causes obesity. Together, this atlas contributes high-resolution PVH spatial and circuit-based gene expression profiles, representing a valuable resource for the field of homeostasis.