Project description:Neurons in the arcuate nucleus (ARC) sense the fed/fasted state and regulate hunger. ARCAgRP neurons release GABA, NPY and the melanocortin-4 receptor (MC4R) antagonist, AgRP, and are activated by fasting1-4. When stimulated, they rapidly and potently drive hunger5,6. ARCPOMC neurons, in contrast, release the MC4R agonist, α-MSH, and are viewed as the counterpoint to ARCAgRP neurons. They are regulated in an opposite fashion and their activity leads to decreased hunger2,4,7. Together, ARCAgRP and ARCPOMC neurons constitute the ARC feeding center. Against this, however, is the finding that ARCPOMC neurons, unlike ARCAgRP neurons, fail to affect food intake over the timescale of minutes to hours following opto- or chemogenetic stimulation5,8. This suggests a rapidly acting component of the ARC satiety pathway is missing. Here, we show that excitatory ARC neurons identified by expression of vesicular glutamate transporter 2 (VGLUT2) and the oxytocin receptor, unlike ARCPOMC neurons, rapidly cause satiety when chemo- or optogenetically manipulated. These glutamatergic ARC projections synaptically converge with GABAergic ARCAgRP projections on MC4R-expressing neurons in the paraventricular hypothalamus (PVHMC4R neurons), which are known to mediate satiety9. ARCPOMC neurons also send dense projections to the PVH. Importantly, the α-MSH they release post-synaptically potentiates glutamatergic synaptic activity onto PVHMC4R neurons – including that emanating from ARCVglut2 neurons. This suggests a means by which α-MSH can bring about satiety – via postsynaptic potentiation of this novel ARCVglut2 to PVHMC4R satiety circuit. Thus, while fast (GABA and NPY) and slow (AgRP) ARC hunger signals are delivered together by ARCAgRP neurons10,11, the temporally analogous satiety signals from the ARC, glutamate and α-MSH, are delivered separately by two parallel, interacting projections (from ARCVGLUT2 and ARCPOMC neurons). Discovery of this rapidly acting excitatory ARC → PVH satiety circuit, and its regulation by α-MSH, provides new insight into regulation of hunger/satiety.
Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other
Project description:Arc is an activity regulated neuronal protein yet little is known about its protein interactions, assembly into multiprotein complexes, role in human disease and cognition. We applied an integrated proteomic and genetic strategy using targeted tagging of a Tandem Affinity Purification (TAP) tag and Venus fluorescent protein into the endogenous Arc gene in mice, biochemical and proteomic characterization of native complexes in wild type and knockout mice, and human genetic analyses of disease and intelligence. TAP tagging enabled efficient purification of complexes and identification of many novel Arcinteracting proteins, of which PSD95 was the most abundant. PSD95 was essential for Arc assembly into 1.5 MDa complexes and activity-dependent recruitment to excitatory synapses. Integrating human genetic data with proteomic data showed postsynaptic Arc- PSD95 complexes are enriched in schizophrenia, intellectual disability, autism and epilepsy mutations and normal variants in intelligence. Arc-PSD95 postsynaptic complexes are a molecular substrate for the convergence of normal and pathological genetic variants impacting on human cognitive function.