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Estrogens play pivotal roles in sexual development, growth, reproduction, and sex differentiation and have been implicated in a number of physiological processes in various tissues. Most of the effects of estrogens are mediated by the estrogen receptors alpha ( ERα), beta ( ERβ), and G protein-coupled receptor 30 ( GPR30). The liver is known to be a target tissue for estrogen signaling, but the physiological role of this signaling is not well characterized. Through analyses of an estradiol (E2)-treated hepatocyte cell line and mice, we showed that E2 signaling controls hepatocyte proliferation. Importantly, our data showed that the E2 signaling that is mediated through ERα is crucial for efficient liver regeneration after partial hepatectomy ( PH). PH rapidly induced marked increases in circulating E2 and ERα transcripts in periportal hepatocytes, well before the onset of hepatocyte proliferation. Taken together, our results indicate that increased E2 is one of the initiating signals that trigger liver regeneration. We suggest that E2 treatment could be beneficial for stimulating liver regeneration in humans. [ABSTRACT FROM AUTHOR]

We report a water-based optical clearing agent, SeeDB, which clears fixed brain samples in a few days without quenching many types of fluorescent dyes, including fluorescent proteins and lipophilic neuronal tracers. Our method maintained a constant sample volume during the clearing procedure, an important factor for keeping cellular morphology intact, and facilitated the quantitative reconstruction of neuronal circuits. Combined with two-photon microscopy and an optimized objective lens, we were able to image the mouse brain from the dorsal to the ventral side. We used SeeDB to describe the near-complete wiring diagram of sister mitral cells associated with a common glomerulus in the mouse olfactory bulb. We found the diversity of dendrite wiring patterns among sister mitral cells, and our results provide an anatomical basis for non-redundant odor coding by these neurons. Our simple and efficient method is useful for imaging intact morphological architecture at large scales in both the adult and developing brains. [ABSTRACT FROM AUTHOR]

Since the discovery of odorant receptors (ORs) in rodents, most ORs have remained orphan receptors. Even for deorphanized ORs in vitro, their in vivo properties are largely unknown. Here, we report odor response profiles of two highly homologous mouse ORs, MOR29A and MOR29B, both in vivo and in vitro. The BAC transgenic mouse was generated, in which olfactory sensory neurons (OSNs) expressing the transgenes MOR29A and MOR29B were differently tagged with IRES-gapECFP and IRES-gapEYFP, respectively. MOR29A- and MOR29B-expressing OSN axons converged on separate but nearby loci on the dorsal surface of the olfactory bulb (OB). Optical imaging of intrinsic signals in the OB identified five different phenyl ethers as candidate ligands for MOR29B. Based on in vitro calcium imaging with the isolated OSNs and luciferase assay with heterologous cells, only guaiacol and vanillin were found to be potent agonists for MOR29A and MOR29B. Because of its accessible glomerular locations in the dorsal OB and defined odor response profiles both in vivo and in vitro, the MOR29A/29B tagging mouse will serve as an excellent tool for studying both odor-signal processing and neural circuitry in the OB. [ABSTRACT FROM AUTHOR]

Sensory information detected by the peripheral nervous system is represented as a topographic map in the brain. It has long been thought that the topography of the map is determined by graded positional cues that are expressed by the target. Here, we analyzed the pre-target axon sorting for olfactory map formation in mice. In olfactory sensory neurons, an axon guidance receptor, Neuropilin-1, and its repulsive ligand, Semaphorin-3A, are expressed in a complementary manner. We found that expression levels of Neuropilin-1 determined both pro-target sorting and projection sites of axons. Olfactory sensory neuron-specific knockout of Semaphorin-3A perturbed axon sorting and altered the olfactory map topography. Thus, pre-target axon sorting plays an important role in establishing the topographic order based on the relative levels of guidance molecules expressed by axons. [ABSTRACT FROM AUTHOR]

The mammalian olfactory system mediates various responses, including aversive behaviours to spoiled foods and fear responses to predator odours. In the olfactory bulb, each glomerulus represents a single species of odorant receptor. Because a single odorant can interact with several different receptor species, the odour information received in the olfactory epithelium is converted to a topographical map of multiple glomeruli activated in distinct areas in the olfactory bulb. To study how the odour map is interpreted in the brain, we generated mutant mice in which olfactory sensory neurons in a specific area of the olfactory epithelium are ablated by targeted expression of the diphtheria toxin gene. Here we show that, in dorsal-zone-depleted mice, the dorsal domain of the olfactory bulb was devoid of glomerular structures, although second-order neurons were present in the vacant areas. The mutant mice lacked innate responses to aversive odorants, even though they were capable of detecting them and could be conditioned for aversion with the remaining glomeruli. These results indicate that, in mice, aversive information is received in the olfactory bulb by separate sets of glomeruli, those dedicated for innate and those for learned responses. [ABSTRACT FROM AUTHOR]

In the mouse olfactory epithelium, there are about ten million olfactory sensory neurons, each expressing a single type of odorant receptor out of ∼1000. Olfactory sensory neurons expressing the same odorant receptor converge their axons to a specific set of glomeruli on the olfactory bulb. How odorant receptors play an instructive role in the projection of axons to the olfactory bulb has been one of the major issues of developmental neurobiology. Recent studies revealed previously overlooked roles of odorant receptor-derived cAMP signals in the axonal projection of olfactory sensory neurons; the levels of cAMP and neuronal activity appear to determine the expression levels of axon guidance/sorting molecules and thereby direct the axonal projection of olfactory sensory neurons. These findings provide new insights as to how peripheral inputs instruct neuronal circuit formation in the mammalian brain. [Copyright &y& Elsevier]

Summary: G-protein-coupled receptors (GPCRs) are known to possess two different conformations, active and inactive, and they spontaneously alternate between the two in the absence of ligands. Here, we analyzed the agonist-independent GPCR activity for its possible role in receptor-instructed axonal projection. We generated transgenic mice expressing activity mutants of the β2-adrenergic receptor, a well-characterized GPCR with the highest homology to odorant receptors (ORs). We found that mutants with altered agonist-independent activity changed the transcription levels of axon-targeting molecules—e.g., Neuropilin-1 and Plexin-A1—but not of glomerular segregation molecules—e.g., Kirrel2 and Kirrel3—thus causing shifts in glomerular locations along the anterior-posterior (A-P) axis. Knockout and in vitro experiments demonstrated that Gs, but not Golf, is responsible for mediating the agonist-independent GPCR activity. We conclude that the equilibrium of conformational transitions set by each OR is the major determinant of expression levels of A-P-targeting molecules. [ABSTRACT FROM AUTHOR]

Arginine, a semi-essential amino acid, is known as one of the most strongest insulin secretagogues in a glucose-dependent manner, but major mechanism is unknown. Arginine induced insulin secretion in mice as well as β cell line, NIT-1, in which more than 90% of intracellular insulin is prionsulin without arginine cultivation. Arginine administration reduced prionsulin amount in 30 s, then insulin is secreted from NIT1 cells. These data indicated that the target factor(s) for arginine-induced insulin secretion located in endoplasmic reticulum (ER). We established the screening system for identifying the arginine mimetics. Brazilian propolis, not Chinese propolis, induced insulin secretion. To identify target factor(s) of arginine induced insulin secretion, our previous study was that nanobeads technology facilitated us to purify chemical-target factors. This time we chose the other way, proinsulin associating factor purification and arginine-immobilized agarose. Three proinsulin associating factors and 5 arginine interacting factors were identified. Among theses factors, Calnexin (CNX) was the only one factor, which belonged to both groups, suggesting that CNX might play a key role in arginine-induced insulin secretion in ER. [ABSTRACT FROM AUTHOR]