SAT-021 Characterizing Melanin-Concentrating Hormone (MCH) Neuron Subpopulations Using an Intersectional Reporter Mouse Line

Abstract Disclosure: L.J. DiLeone: None. M.S. Antony: None. A.C. Jackson: None. Melanin-concentrating hormone (MCH; encoded for by the Pmch gene) is a neuropeptide expressed by a unique population of neuromodulatory neurons, localized in the mammalian lateral hypothalamic area (LHA). MCH neurons play a pivotal role in a diversity of both sleep- and wake-related innate behaviors such as the regulation of rapid-eye movement (REM) sleep, feeding, memory consolidation, and exploratory behavior. Despite its functional heterogeneity, neurochemical and molecular diversity among MCH neurons is poorly understood. Building upon previous anatomical and developmental studies, our single-cell RNA sequencing of the LHA confirmed that MCH neurons exhibit molecular heterogeneity in the form of two major subpopulations, defined by multiple markers. Notably, one subset of MCH neurons exhibits an enrichment in transcripts expressing cocaine- and amphetamine-regulated transcript (Cartpt) and tachykinin receptor-3 (Tacr3). We hypothesize that MCH neurons are molecularly diverse, with distinct subpopulations differentially contributing to their specialized roles in regulating opposing behaviors through unique anatomical projections. Here, we describe an intersectional genetic strategy for gaining genetic access to a molecularly distinct MCH subpopulation in mice. We crossed a Pmch-Cre; Tacr3-Flpo dual-recombinase mouse to an intersectional reporter line, RC::FLTG to generate a Pmch-Cre; Tacr3-Flpo; RC::FLTG mouse which exhibits fluorescent labelling of MCH(Tacr3+) cell bodies and axons. We first characterized the specificity of the intersectional targeting within the LHA and the differential spatial distribution of labeled vs. unlabeled MCH+ neurons within the LHA. We then identified unique anatomical projection targets of labeled MCH(Tacr3+) neurons within the forebrain and midbrain. Ultimately, this approach will enable us to identify molecularly distinct MCH subpopulations and their anatomical projections, providing important groundwork for future studies aimed at understanding the roles of these neuronal subpopulations in distinct behaviors. Presentation: Saturday, July 12, 2025