Biology subjects

Chee, M. J.

Publications and source records attributed to Chee, M. J..

2 recordsLinked to original sources

bioRxiv2019

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

Melanin-concentrating hormone (MCH) is a ubiquitous vertebrate neuropeptide predominantly synthesized by neurons of the diencephalon that can act through two G protein-coupled receptors, called MCHR1 and MCHR2. The expression of Mchr1 has been investigated in both rats and mice, but its synthesis remains poorly described. After identifying an antibody that detects MCHR1 with high specificity, we employed immunohistochemistry to map the distribution of MCHR1 in the CNS of rats and mice. Multiple neurochemical markers were also employed to characterize some of the neuronal populations that synthesize MCHR1. Our results show that MCHR1 is abundantly found in a sensory subcellular structure called the neuronal primary cilium, which has been associated with the detection of free neurochemical agents released to act through volume transmission. Ciliary MCHR1 was found in a wide range of areas, including the olfactory bulb, cortical mantle, striatum, hippocampal formation, amygdala, midline thalamic nuclei, periventricular hypothalamic nuclei, and midbrain areas. No differences were observed between male and female mice, and rats and mice diverged in two key areas: the caudate-putamen nucleus and the subgranular zone of the dentate gyrus. Ciliary MCHR1 was found in close association to several neurochemical markers, including tyrosine hydroxylase, calretinin, kisspeptin, estrogen receptor, oxytocin, vasopressin, and corticotropin-releasing factor. Given the role of neuronal primary cilia in sensing free neurochemical messengers in the extracellular fluid, the widespread distribution of ciliary MCHR1, and the diverse neurochemical populations who synthesize MCHR1, our data indicates that volume transmission may play a prominent role in the normal function of the MCH system.

neuroscience↗

bioRxiv2019

Distributions of hypothalamic neuron populations co-expressing tyrosine hydroxylase and the vesicular GABA transporter in the mouse

The hypothalamus contains catecholaminergic neurons marked by the expression of tyrosine hydroxylase (TH). As multiple chemical messengers coexist in each neuron, we determined if hypothalamic TH-immunoreactive (ir) neurons express glutamate or GABA. We used Cre/loxP recombination to express enhanced GFP fluorescence (EGFP) in neurons that express the vesicular glutamate (vGLUT2) or GABA transporter (vGAT), then determined TH immunoreactivity in glutamatergic or GABAergic neurons, respectively. EGFP-positive vGLUT2 neurons were not TH-ir. However, discrete TH-ir signals colocalized with EGFP-positive vGAT neurons, which we validated by in situ hybridization for Vgat mRNA. In order to contextualize the observed pattern of TH+EGFP colocalization in vGAT neurons, we first performed Nissl-based parcellation and plane-of-section analysis, and then mapped the distribution of TH-ir vGAT neurons onto atlas templates from the Allen Reference Atlas (ARA) of the mouse brain. TH-ir vGAT neurons were distributed throughout the rostrocaudal extent of the hypothalamus. Within the ARA ontology of gray matter regions, TH-ir neurons localized primarily to the periventricular hypothalamic zone, periventricular hypothalamic region, and lateral hypothalamic zone. There was a very strong presence of EGFP fluorescence in TH-ir neurons across all brain regions, but the most striking colocalization was found in the zona incerta (ZI) - a region assigned to the hypothalamus in the ARA - where every TH-ir neuron was EGFP-positive. Neurochemical characterization of these ZI neurons revealed that they display immunoreactivity for dopamine but not dopamine {beta}-hydroxylase. In aggregate, these findings indicate the existence of a novel hypothalamic population in the mouse that may signal through the release of GABA and/or dopamine.

neuroscience↗