1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

457 Poster Developmental, Neurogenesis, and ConsumerResearchNESTIN IS EXPRESSED BY A SUBSET OF EMBRYONIC ANDPOSTNATAL OE PROGENITORSMurdoch B. 1 , Janzen N. 1 , Roskams A. 1 1 Zoology, University of BritishColumbia, Vancouver, British Columbia, CanadaThe olfactory neuroepithelium (OE) generates new olfactory receptorneurons (ORNs) into adulthood. We do not know if the most pluripotentprogenitors in adult OE are identical to, or adult progeny, of, embryonicprogenitors that first create the OE, or if progenitors are zonallycommitted. Nestin, which is found in CNS neural stem cells, isexpressed by radial glia-like cells (RGLCs) in embryonic (E13.5) andpostnatal day 5 (P5), but not adult, OE. These RGLCs are highly mitoticdevelopmentally, but rare in P5 OE. Nestin+ RGLCs co-express theglutamate transporter NGLAST, but not a neurogenic radial glialprotein, brain lipid binding protein (BLBP), which is exclusivelysegregated to the OEC lineage. Clonal neural progenitor assays in vitrogenerate not neurospheres, but semi-adherent, rapidly expandingcolonies from E13.5 OE, whereas P5 and adult OE generated adherentcolonies and neurospheres. Embryonic OE semi-adherent coloniescontain a high proportion of nestin+, neuronal/glial lineage negativecells, passage extensively and produce neurons and glia. OE progenitorsprogressively decrease their ability to passage from E13.5 to P5 andadult. Decreased passaging of P5 OE is accompanied by an increasedfrequency of Nestin+ OECs within primary spheres. Using a geneticlineage tracing strategy, nestin-cre:Z/EG double-transgenic miceindicate that ORNs in restricted zones of the OE and vomeronasal organ(VNO) are derived from a subset of nestin expressing precursors. Theseresults indicate that the OE progenitor identity and self-renewalcapacity changes during aging, and that defined zones are generated inembryonic development through defined progenitor lineages.458 Poster Developmental, Neurogenesis, and ConsumerResearchHORIZONTAL BASAL CELLS ARE MULTIPOTENT NEURALPROGENITORS IN OLFACTORY EPITHELIUMLeung C.T. 1 , Reed R.R. 1 1 Molecular Biology and Genetics, JohnsHopkins University, Baltimore, MDThe continual neurogenesis and remarkable regenerative capacity ofthe olfactory epithelium (OE) suggest that a stem cell population islikely to persist in this system. Developmental and regenerative studieshave located the potential OE stem cells among a population of basalcells that includes the GBCs (globose basal cells) and HBCs (horizontalbasal cells). Their respective roles remain controversial. In culture, theability of HBCs to self-renew and give rise to neuronal and nonneuronalcell types supports HBCs as potential stem cell candidates.However, the in vivo roles of HBCs remain elusive, due to theirquiescent nature that renders traditional methods to study cell lineageinefficient and non-specific. We examined the cellular contributions ofHBCs to OE cell populations in normal and lesioned epithelium using afate-mapping strategy based on an HBC-specific Cre-LoxP system. Ourresults confirmed that HBCs divide infrequently and retain theiridentities in intact OE. HBCs remain quiescent in OE even afterbulbectomy-induced neuronal ablation. Intriguingly, after acute OElesion, HBCs are highly proliferative and give rise to all OE cell types,including GBCs, olfactory receptor neurons, sustentacular cells and ductcells. Together, our data suggest that HBCs are multipotent neuralprogenitors and lead to a model in which the HBC and GBCpopulations play distinct roles in the cellular dynamics associated withOE development and maintenance.459 Poster Developmental, Neurogenesis, and ConsumerResearchMACROPHAGE DEPLETION IN MURINE OLFACTORYEPITHELIUM LEADS TO DECREASED NEUROGENESISBorders A.S. 1 , Getchell M.L. 2 , Etscheidt J. 1 , Cohen D.A. 3 , GetchellT.V. 1 1 Physiology, University of Kentucky, Lexington, KY; 2 Anatomyand Neurobiology, University of Kentucky, Lexington, KY;3 Microbiology and Immunology, University of Kentucky, Lexington, KYInduced apoptosis of olfactory sensory neurons (OSNs) by olfactorybulbectomy (OBX) leads to the activation of resident macrophageswithin the olfactory epithelium (OE). These macrophages phagocytosethe degenerating OSNs and subsequently secrete chemokines, mostnotably MIP-1α, that recruit additional macrophages into the OE. Thisinfiltration of macrophages has been shown to parallel the levels ofbasal cell proliferation, which leads to the differentiation and maturationof OSNs. Here we examined the effects of reduced macrophage levelsin the OE on olfactory neurogenesis 48 hr post-OBX by inducingapoptosis in macrophages using liposome-encapsulated clodronate(dichloromethylene bisphosphonate; Van Rooijen, J. Immunol. Methods174:83, 1994). We found a 38% and 35% reduction in OE macrophagesin sham and OBX mice, respectively, compared to liposome-treatedcontrols following intranasal and intravenous administration. Thereduction in macrophages was accompanied by a decrease in OEthickness and basal cell proliferation in sham and OBX mice comparedto controls. In addition, there appeared to be fewer mature OSNs inclodronate-treated mice. These results indicate that macrophagesregulate the integrity of normal and target-ablated murine OE byinfluencing basal cell proliferation and replacement of mature OSNs.Supported by: NIH-T32-DC000065 (ASB), NIH-AG16824 (TVG),NIH-HL69459 (DAC).460 Poster Developmental, Neurogenesis, and ConsumerResearchMOUSE MODEL OF A HUMAN GENE POLYMORPHISM INTHE PRODOMAIN OF BDNF (VAL66MET) ALTERSNEUROGENESIS IN THE OLFACTORY SYSTEMBath K.G. 1 , Chen Z. 1 , Jing D. 1 , Lee F.S. 1 1 Psychiatry, Weill MedicalCollege of Cornell, New York, NYNeurotrophins are well known mediators of cellular division andsurvival throughout development. In adults, BDNF is an importantregulator of synaptic connectivity, synaptic remodeling, and neuronalsurvival. We have developed a mouse line that carries a naturallyoccurring variation in the BDNF protein found to occur in humans, avaline (val) to methionine (met) substitution at position 66 in theprodomain (val66met). Approximately 30% of Caucasians and 50% ofAsians carry the met allele. Human carriers of the met variant have beenshown to have subtle impairments in hippocampal dependent memorytasks, have smaller hippocampal volume, and potentially be predisposedto the development of a suite of psychiatric disorders compared tosubjects that are homozygous for the val allele. Our lab is interested ininvestigating the effect of this gene variant on hippocampal andolfactory bulb morphology, cognition, and behavior. We describe heredifferences in rates of cell division and survival between animals ofdiffering genotypes.115