A CreER mouse to study melanin concentrating hormone signaling in the developing brain

Abstract

The neuropeptide, melanin concentrating hormone (MCH), and its G protein-coupled receptor, melanin concentrating hormone receptor 1 (Mchr1), are expressed centrally in adult rodents. MCH signaling has been implicated in diverse behaviors such as feeding, sleep, anxiety, as well as addiction and reward. While a model utilizing the Mchr1 promoter to drive constitutive expression of Cre recombinase (Mchr1-Cre) exists, there is a need for an inducible Mchr1-Cre to determine the roles for this signaling pathway in neural development and adult neuronal function. Here, we generated a BAC transgenic mouse where the Mchr1 promotor drives expression of tamoxifen inducible CreER recombinase. Many aspects of the Mchr1-Cre expression pattern are recapitulated by the Mchr1-CreER model, though there are also notable differences. Most strikingly, compared to the constitutive model, the new Mchr1-CreER model shows strong expression in adult animals in hypothalamic brain regions involved in feeding behavior but diminished expression in regions involved in reward, such as the nucleus accumbens. The inducible Mchr1-CreER allele will help reveal the potential for Mchr1 signaling to impact neural development and subsequent behavioral phenotypes, as well as contribute to the understanding of the MCH signaling pathway in terminally differentiated adult neurons and the diverse behaviors that it influences.

Hedgehog Pathway Activation Alters Ciliary Signaling in Primary Hypothalamic Cultures

“…Similar results were observed using quantitative PCR for hypothalamic gene expression (Figure 2C). To further confirm that neurons from multiple hypothalamic regions were present in vitro , we utilized Cre recombinase inducible alleles with a tdTomato fluorescent reporter for both POMC and Mchr1 expressing neurons which are found in the ARC and PVN in vivo and reporter positive cells were observed in vitro (Berglund et al, 2013; Engle et al, 2018; Figure 2D). Together, these results suggest that similar to cultured hippocampal primary neurons, hypothalamus derived neurons display expression patterns like those observed in vivo .…”

“…Wildtype primary cultures were obtained from C57BL/6J mice from Jackson Laboratories. Cre lines Pomc-CreER (generously provided by Joel K. Elmquist and Chen Liu) and Mchr1-CreER have both been previously described (Berglund et al, 2013; Engle et al, 2018). All procedures and approaches were approved by the Institutional Animal Care and Use Committee at Indiana University-Purdue University School of Science, Indianapolis.…”

Neuron-specific cilia loss alters locomotor responses to amphetamine

“…Notably, cilia in midbrain dopaminergic and NAc GABAergic neurons express different complements of neuromodulatory receptors. For example, both MCHR1 and GPR88 are enriched in cilia in NAc, but are not detected in cilia on midbrain dopaminergic neurons [16,17,25] The results show that cilia ablation on either GAD2-GABAergic or dopaminergic neurons attenuates the locomotor stimulant effect of acute amphetamine. In contrast, cilia ablation on GAD2-GABAergic neurons enhances sensitization of the locomotor stimulant effect of repeated amphetamine, whereas ablation on dopaminergic neurons has no effect.…”

The distribution of neuronal primary cilia immunoreactive to melanin-concentrating hormone receptor 1 (MCHR1) in the murine prosencephalon

“…Gene reporters and in situ hybridization have been used to investigate the expression of Mchr1 in the mouse brain (Chee et al 2013;Engle et al 2018). Our distribution of MCHR1 immunoreactivity is mostly similar to what has been described in those works, including the olfactory areas, a similar pattern of cortical distribution, very dense labeling of the islands of Calleja, preeminent labeling in the pyramidal layer of the hippocampal formation and induseum griseum, no labeling of the medial septal nucleus, low labeling of thalamic nuclei, and weak to moderate labeling of the zona incerta and amygdala.…”

“…In both cases, only male specimens were used, and both works describe widespread expression/synthesis of MCHR1. The next wave of works then focused on mice, through the use of gene reporters (Chee et al 2013;Engle et al 2018). Despite an exhaustive investigation and detailed description of the gene reporter distribution, the experimental model of gene reporters cannot inform the subcellular localization of the protein product that results from the investigated gene.…”