1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

13 Symposium Chemosensory Receptors SatelliteODORANT RECEPTORS WITH UNIQUE FEATURESBreer H. 1 , Strotmann J. 1 1 Institute of Physiology, University ofHohenheim, Stuttgart, GermanyThe repertoire of odorant receptors (ORs) in mammals comprisesaround 1000 different subtypes; despite their enormous sequencevariability most of them share mainly common features, includingmembrane topology and expression pattern. However, some of the ORtypes appear to be unique. Receptors of the OR37 subfamily displayquite distinguished features, including an extended third extracellularloop and a clustered expression pattern. These receptors are only foundin mammals and in contrast to OR genes in general, the genes encodingOR37 receptors appear to be under negative selection. Theseoutstanding properties suggest that OR37 receptors are specificallytuned to distinct chemical signals. Also the more recently discoveredreceptor mOR256-17 is characterized by exceptional properties. It isexpressed in a larger number of sensory neurons than other ORs,especially during prenatal development. The onset of expression occursalready at embryonic day 10 (E10), thus almost one day prior to otherOR types. The axons of olfactory cells expressing mOR256-17 reachthe rostral forebrain at E13, whereas the axons of other OR-cells targetthe presumptive olfactory bulb not before E14.5/15. In addition,mOR256-17 is not only expressed in sensory neurons of the olfactoryepithelium, but also in a substantial subpopulation of non-sensory cellswhich is located in the cribriform mesenchyme during a defined phaseof prenatal development. These 'extra-epithelial' mOR256-17expressing cells are closely associated with olfactory axons and appearto be intimately involved in the initiation and establishment of thewiring patterns in the olfactory system. This work was supported by theDeutsche Forschungsgemeinschaft.15 Symposium Chemosensory Receptors SatelitteCOMPLEXITY AND MODULARITY IN THE REGULATIONOF CHEMORECEPTOR GENE EXPRESSION IN C. ELEGANSVan Der Linden A.M. 1 , Nolan K. 2 , Sengupta P. 1 1 Biology, BrandeisUniversity, Waltham, MA; 2 School of Law, University of California,Berkeley, CAEach C. elegans chemosensory neuron expresses multiplechemoreceptor (CR) genes. A simple mechanism by which nematodescan rapidly modulate their sensory behaviors in response to changingenvironmental conditions is via modulation of expression of subsets ofCR genes in individual chemosensory neurons. Previously, we andothers showed that the expression of CRs can be altered in response toneuronal activity and environmental cues. This provides a simplemechanism by which C. elegans can rapidly alter its sensory behaviorsin response to changing conditions. What are the molecular mechanismsregulating expression of CR genes? We previously showed thatmutations in the salt-inducing kinase related kin-29 gene result indownregulation of expression of a subset of CR genes. To define themechanisms of KIN-29 function, we carried out genetic suppressorscreens and isolated mutations in the transcription factor mef-2 and theclass II histone deacetylase hda-4 genes. MEF2 and class II HDACshave been shown to regulate gene expression in response to intracellularsignaling and electrical activity. We dissected the cis-regulatorysequences of KIN-29-regulated CRs and showed that MEF-2 bindsdirectly to CR gene promoters, and that MEF-2 binding sequences areboth necessary and sufficient to confer KIN-29-mediated regulationonto CR genes. Modulation of CR gene expression requiresphosphorylation of HDA-4, and we show that neuronal activity interactswith the KIN-29-regulated pathway to modulate CR gene expression.Taken together, our findings suggest a role for chromatin remodeling inresponse to activity and other signals in the regulation of CR geneexpression.14 Symposium Chemosensory Receptors SatelliteSymposiumEVOLUTIONAL AND BIOLOGICAL CHARACTERIZATIONOF THE MOUSE ESP FAMILYTouhara K. 1 1 University of Tokyo, Chiba, JapanWe discovered a male-specific 7 kDa secreting peptide, ESP1, thatelicited an electrical response in V2R-expressing vomeronasal sensoryneurons (VSNs) in mice. ESP1 secreted in tears appears to betransferred to the female vomeronasal organ (VNO) through physicalcontact upon investigation of the facial areas, which reminisce LarryKatz´s finding reported in Science 2003. ESP1 turned out to be amember of a previously-unrecognized large family clustered inproximity to the class I MHC region. I herein report comprehensivegenomic analysis of the ESP family in rodents and other species anddiscuss about an evolutional aspect of the family. The genomic andcDNA analyses suggest that a single peptide is encoded by each genewith a three-exon/two-intron structure. Expression profile revealed thatthere existed male- and female-specific ESPs. Electro-vomeronasogramwas performed for several ESP family peptides, providing insight intofunction of the family. We previously demonstrated that ESP1-inducedc-Fos-positive VSNs expressed a V2R gene recognized by the V2Rpprobe that potentially hybridized with several V2R genes. Wenarrowed down to one V2R, named V2Rp5, expressed in 100% of c-Fos-positive VSNs. The results suggest that ESP1 is recognized by asingle type of V2R, and thereby, pheromone recognition in VNOappears to be narrowly tuned and highly specific. [supported byPROBRAIN Japan]16 Symposium Chemosensory Receptors SatelliteSymposiumATYPICAL MEMBRANE TOPOLOGY AND HETEROMERICFUNCTION OF DROSOPHILA ODORANT RECEPTORS INVIVOBenton R. 1 , Sachse S. 1 , Michnick S. 2 , Vosshall L. 1 1 RockefellerUniversity, New York, NY; 2 University of Montreal, Montreal, Quebec,CanadaDrosophila olfactory sensory neurons (OSNs) each express twoodorant receptors (ORs): a divergent member of the OR family and thehighly conserved, broadly expressed receptor OR83b. OR83b isessential for olfaction in vivo and enhances OR function in vitro, but themolecular mechanism by which it acts is unknown. Here wedemonstrate that OR83b heterodimerizes with conventional ORs earlyin the endomembrane system in OSNs, couples these complexes to theconserved ciliary trafficking pathway, and is essential to maintain theORs within the sensory cilia, where odor signal transduction occurs.The OR/OR83b complex is necessary and sufficient to promotefunctional reconstitution of odor-evoked signaling in sensory neuronsthat normally respond only to carbon dioxide. Unexpectedly, unlike allknown vertebrate and nematode chemosensory receptors, we find thatDrosophila ORs and OR83b adopt a novel membrane topology withtheir N-termini and the most conserved loops in the cytoplasm. Theseloops mediate direct association of ORs with OR83b. Our results revealthat OR83b is a universal and integral part of the functional OR inDrosophila. This atypical heteromeric and topological design appears tobe an insect-specific solution for odor recognition, making theOR/OR83b complex an attractive target for the development of highlyselective insect repellents to disrupt olfactory-mediated host-seekingbehaviors of insect disease vectors.4