Biology subjects

Miller, P. A.

Publications and source records attributed to Miller, P. A..

3 recordsLinked to original sources

bioRxiv2026

Intersectional genetic targeting of molecularly distinct melanin-concentrating hormone neuron subpopulations reveals distinct and overlapping subcircuit architecture

The lateral hypothalamic area (LHA) coordinates crucial and innate behaviors through heterogeneous yet poorly understood neuronal populations and circuits. Neurons that produce melanin-concentrating hormone (MCH; encoded by the Pmch gene) are primarily localized in the LHA and contribute to feeding, sleep-wake regulation, memory, and reward-associated behaviors. Building on foundational anatomical studies, our single-cell transcriptomic analysis of the LHA identified markers distinguishing at least two transcriptionally distinct MCH subpopulations. These subpopulations are distinguished by the selective enrichment of the Tacr3 and Cartpt transcripts, with each comprising approximately half of the total MCH population. However, these subpopulations remain poorly understood owing to limited genetic targeting tools. We hypothesized that MCH neurons operate through functionally distinct, parallel subcircuits that exhibit unique neuroanatomical projections. In this study, we leveraged Pmch and Tacr3 expression to intersectionally dissociate these neurons into Type I MCH (Pmch+/Tacr3+) and Type II MCH (Pmch+/Tacr3-) subpopulations. We first validated a Tacr3-Flpo mouse line for the genetic targeting of the Type I MCH subpopulation. We then generated an intersectional Type I MCH neuron reporter line to visualize Type I axonal projections. In parallel, we injected a dual recombinase mouse line with the intersectional genetic targeting viruses, Conditional Viral Expression by Ribozyme Guided Degradation (ConVERGD), and identified overlapping and distinct projections by Type I and Type II MCH neurons using fluorescence microscopy, super-resolution imaging, and high-spatial resolution fiber mapping. Overall, these data establish the first subpopulation-resolved anatomical framework for molecularly distinct Type I and Type II MCH subcircuits, thus establishing a foundation for future circuit-level functional studies.

neuroscience↗

bioRxiv2023

Neuroanatomical, electrophysiological, and morphological characterization of melanin-concentrating hormone cells coexpressing cocaine- and amphetamine-regulated transcript

Melanin-concentrating hormone (MCH) cells in the hypothalamus regulate fundamental physiological functions like energy balance, sleep, and reproduction. This diversity may be ascribed to the neurochemical heterogeneity among MCH cells. One prominent subpopulation of MCH cells coexpresses cocaine- and amphetamine-regulated transcript (CART), and as MCH and CART can have opposing actions, MCH/CART+ and MCH/CART- cells may differentially modulate behavioural outcomes. However, it is not known if there are differences in cellular properties underlying their functional differences, thus we compared the neuroanatomical, electrophysiological, and morphological properties of MCH cells in male and female Mch-cre;L10-Egfp reporter mice. Half of MCH cells expressed CART and were most prominent in the medial hypothalamus. Whole-cell patch-clamp recordings revealed differences in their passive and active membrane properties in a sex-dependent manner. Female MCH/CART+ cells had lower input resistances, but male cells largely differed in their firing properties. All MCH cells increased firing when stimulated, but their firing frequency decreases with sustained stimulation. MCH/CART+ cells showed stronger spike rate adaptation than MCH/CART- cells. The kinetics of excitatory events at MCH cells also differed by cell type, as the rising rate of excitatory events was slower at MCH/CART+ cells. By reconstructing the dendritic arborization of our recorded cells, we found no sex differences, but male MCH/CART+ cells had less dendritic length and fewer branch points. Overall, distinctions in topographical division and cellular properties between MCH cells add to their heterogeneity and help elucidate their response to stimuli or effect on modulating their respective neural networks.

neuroscience↗

bioRxiv2023

Regulation of the mouse ventral tegmental area by melanin-concentrating hormone

Melanin-concentrating hormone (MCH) acts via its sole receptor MCHR1 in rodents and is an important regulator of homeostatic behaviors like feeding, sleep, and mood to impact overall energy balance. The loss of MCH signaling by MCH or MCHR1 deletion produces hyperactive mice with increased energy expenditure, and these effects are consistently associated with a hyperdopaminergic state. We recently showed that MCH suppresses dopamine release in the nucleus accumbens, which principally receives dopaminergic projections from the ventral tegmental area (VTA), but the mechanisms underlying MCH-regulated dopamine release are not clearly defined. MCHR1 expression is widespread and includes dopaminergic VTA cells. However, as the VTA is a neurochemically diverse structure, we assessed Mchr1 gene expression at glutamatergic, GABAergic, and dopaminergic VTA cells and determined if MCH inhibited the activity of VTA cells and/or their local microcircuit. Mchr1 expression was robust in major VTA cell types, including most dopaminergic (78%) or glutamatergic cells (52%) and some GABAergic cells (38%). Interestingly, MCH directly inhibited dopaminergic and GABAergic cells but did not regulate the activity of glutamatergic cells. Rather, MCH produced a delayed increase in excitatory input to dopamine cells and a corresponding decrease in GABAergic input to glutamatergic VTA cells. Our findings suggested that MCH may acutely suppress dopamine release while disinhibiting local glutamatergic signaling to restore dopamine levels. This indicated that the VTA is a target of MCH action, which may provide bidirectional regulation of energy balance. Significance StatementRole of melanin-concentrating hormone (MCH) on energy balance may converge on the dopamine system via the mesolimbic pathway, as loss of MCH or MCH receptor (MCHR1) signaling increases hyperactivity and energy expenditure associated with a hyperdopaminergic state. MCH can suppress dopamine release within the mesolimbic pathway, but its underlying mechanism is not known. We thus determined if MCH could inhibit dopamine release through direct actions within the ventral tegmental area (VTA). We found that MCH directly inhibited dopaminergic VTA cells, but MCH also disinhibited excitatory input to dopamine cells. Therefore, we showed that the VTA is a putative target site supporting dopamine-dependent actions of MCH.

neuroscience↗