NR4A Nuclear Receptors Support Memory Enhancement by Histone Deacetylase Inhibitors

The formation of a long-lasting memory requires a transcription-dependent consolidation period that converts a short-term memory into a long-term memory. Nuclear receptors compose a class of transcription factors that regulate diverse biological processes, and several nuclear receptors have been implicated in memory formation. Here, we examined the potential contribution of nuclear receptors to memory consolidation by measuring the expression of all 49 murine nuclear receptors after learning. We identified 13 nuclear receptors with increased expression after learning, including all 3 members of the Nr4a subfamily. These CREB-regulated Nr4a genes encode ligand-independent “orphan” nuclear receptors. We found that blocking NR4A activity in memory-supporting brain regions impaired long-term memory but did not impact short-term memory in mice. Further, expression of Nr4a genes increased following the memory-enhancing effects of histone deacetylase (HDAC) inhibitors. Blocking NR4A signaling interfered with the ability of HDAC inhibitors to enhance memory. These results demonstrate that the Nr4a gene family contributes to memory formation and is a promising target for improving cognitive function

Quantitative real-time PCR protocol for analysis of nuclear receptor signaling pathways-0

<p><b>Copyright information:</b></p><p>Taken from "Quantitative real-time PCR protocol for analysis of nuclear receptor signaling pathways"</p><p>Nuclear Receptor Signaling 2003;1():-.</p><p>Published online 23 Dec 2003</p><p>PMCID:PMC1402222.</p><p>Copyright © 2003, Bookout and Mangelsdorf. This is an open-access article distributed under the terms of the Creative Commons Non-Commercial Attribution License, which permits unrestricted non-commercial use distribution and reproduction in any medium, provided the original work is properly cited. </p

Quantitative real-time PCR protocol for analysis of nuclear receptor signaling pathways-1

<p><b>Copyright information:</b></p><p>Taken from "Quantitative real-time PCR protocol for analysis of nuclear receptor signaling pathways"</p><p>Nuclear Receptor Signaling 2003;1():-.</p><p>Published online 23 Dec 2003</p><p>PMCID:PMC1402222.</p><p>Copyright © 2003, Bookout and Mangelsdorf. This is an open-access article distributed under the terms of the Creative Commons Non-Commercial Attribution License, which permits unrestricted non-commercial use distribution and reproduction in any medium, provided the original work is properly cited. </p

Microrna Let-7 Regulates 3T3-L1 Adipogenesis

Differentiation of 3T3-L1 cells into adipocytes involves a highly orchestrated series of events including clonal expansion, growth arrest, and terminal differentiation. The mechanisms coordinating these different steps are not yet fully understood. Here we investigated whether microRNAs (miRNAs) play a role in this process. Microarray analysis was performed to detect miRNA expression during 3T3-L1 preadipocyte differentiation. Several miRNAs, including let-7, were up-regulated during 3T3-L1 adipogenesis. Ectopic introduction of let-7 into 3T3-L1 cells inhibited clonal expansion as well as terminal differentiation. The mRNA encoding high-mobility group AT-hook 2 (HMGA2), a transcription factor that regulates growth and proliferation in other contexts, was inversely correlated with let-7 levels during 3T3-L1 cell adipogenesis, and let-7 markedly reduced HMGA2 concentrations. Knockdown of HMGA2 inhibited 3T3-L1 differentiation. These results suggest that let-7 plays an important role in adipocyte differentiationandthat itdoesso in partbytargetingHMGA2,thereby regulating the transition from clonal expansion to terminal differentiation. Copyright © 2009 by The Endocrine Society

Expression Profiling Of Nuclear Receptors In Human And Mouse Embryonic Stem Cells

Nuclear receptors (NRs) regulate gene expression in essential biological processes including differentiation and development. Here we report the systematic profiling of NRs in human and mouse embryonic stem cell (ESC) lines and during their early differentiation into embryoid bodies. Expression of the 48 human and mouse NRs was assessed by quantitative real-time PCR. In general, expression of NRs between the two human cell lines was highly concordant, whereas in contrast, expression of NRs between human and mouse ESCs differed significantly. In particular, a number of NRs that have been implicated previously as crucial regulators of mouse ESC biology, including ERRβ, DAX-1, and LRH-1, exhibited diametric patterns of expression, suggesting they may have distinct species-specific functions. Taken together, these results highlight the complexity of the transcrip- tional hierarchy that exists between species and governs early development. These data should provide a unique resource for further exploration of the species-specific roles of NRs in ESC self-renewal and differentiation.Copyright © 2009 by The Endocrine Society

PPARg mRNA in the adult mouse hypothalamus: distribution and regulation in response to dietary challenges

Peroxisome proliferator-activated receptor gamma (PPARg) is a ligand-activated transcription factor that was originally identified as a regulator of peroxisome proliferation and adipocyte differentiation. Emerging evidence suggests that functional PPARg signaling also occurs within the hypothalamus. However, the exact distribution and identities of PPARg-expressing hypothalamic cells remains under debate. The present study systematically mapped PPARg mRNA expression in the adult mouse brain using in situ hybridization histochemistry. PPARg mRNA was found to be expressed at high levels outside the hypothalamus including the neocortex, the olfactory bulb, the organ of the vasculosum of the lamina terminalis, and the subfornical organ. Within the hypothalamus, PPARg was present at moderate levels in the suprachiasmatic nucleus and the ependymal of the 3rd ventricle. In all examined feeding-related hypothalamic nuclei, PPARg was expressed at very low levels that were close to the limit of detection. Using qPCR techniques, we demonstrated that PPARg mRNA expression was upregulated in the suprachiasmatic nucleus in response to fasting. Double in situ hybridization further demonstrated that PPARg was primarily expressed in neurons. Collectively, our observations provide a comprehensive map of PPARg distribution and regulation in the intact adult mouse hypothalamus

Brain SIRT1: anatomical distribution and regulation by energy availability

SIRT1 is a nicotinamide adenosine dinucleotide-dependent deacetylase that orchestrates key metabolic adaptations to nutrient deprivation in peripheral tissues. SIRT1 is induced also in the brain by reduced energy intake. However, very little is known about SIRT1 distribution and the biochemical phenotypes of SIRT1-expressing cells in the neuraxis. Unknown are also the brain sites in which SIRT1 is regulated by energy availability and whether these regulations are altered in a genetic model of obesity. To address these issues, we performed in situ hybridization histochemistry analyses and found that Sirt1 mRNA is highly expressed in metabolically relevant sites. These include, but are not limited to, the hypothalamic arcuate, ventromedial, dorsomedial, and paraventricular nuclei and the area postrema and the nucleus of the solitary tract in the hindbrain. Of note, our single-cell reverse transcription-PCR analyses revealed that Sirt1 mRNA is expressed in pro-opiomelanocortin neurons that are critical for normal body weight and glucose homeostasis. We also found that SIRT1 protein levels are restrictedly increased in the hypothalamus in the fasted brain. Of note, we found that this hypothalamic-specific, fasting-induced SIRT1 regulation is altered in leptin-deficient, obese mice. Collectively, our findings establish the distribution of Sirt1 mRNA throughout the neuraxis and suggest a previously unrecognized role of brain SIRT1 in regulating energy homeostasis. </p

Nav1.8 neurons are involved in limiting acute phase responses to dietary fat

Objective and methods: Metabolic viscera and their vasculature are richly innervated by peripheral sensory neurons. Here, we examined the metabolic and inflammatory profiles of mice with selective ablation of all Nav1.8-expressing primary afferent neurons. Results: While mice lacking sensory neurons displayed no differences in body weight, food intake, energy expenditure, or body composition compared to controls on chow diet, ablated mice developed an exaggerated inflammatory response to high-fat feeding characterized by bouts of weight loss, splenomegaly, elevated circulating interleukin-6 and hepatic serum amyloid A expression. This phenotype appeared to be directly mediated by the ingestion of saturated lipids. Conclusions: These data demonstrate that the Nav1.8-expressing afferent neurons are not essential for energy balance but are required for limiting the acute phase response caused by an obesogenic diet