1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

477 Poster Developmental, Neurogenesis, and ConsumerResearchFORMATION OF THE OLFACTORY PLACODE IN THEZEBRAFISH, DANIO RERIOHarden M.V. 1 , Yang Z. 2 , Lin S. 2 , Whitlock K.E. 1 1 Molecular Biologyand Genetics, Cornell University, Ithaca, NY; 2 Molecular, Cellular andDevelopmental Biology, University of California, Los Angeles, CAIn zebrafish, the olfactory placodes are formed by a convergence oftwo fields of cells located on either side of the developing neural tube(Whitlock and Westerfield, 2000). In order to determine the extent ofcell mixing during formation of the olfactory placodes and cranialneural crest derived structures of the face, we are visualizing cellmovements in the developing embryo. Using a transgenic lineexpressing GFP we are able to visualize the neural crest cells in vivo. Atapproximately 13 hours post fertilization, the neural crest cells migrateanteriorly as a group and separate at the anterior end of the neural tube.Some neural crest cells appear to migrate to the region of the formingolfactory placodes. We are generating a transgenic line that expressesRFP in the olfactory placode fields. By generating animals carryingboth the neural crest GFP and olfactory placode RFP expression we willbe able to visualize the movements of both of these cell types duringdevelopment. Our investigations will provide insight into how theolfactory placode and the neural crest fields mix together duringdevelopment to form the nose. Support: NIH DC0421801 (KEW),Graduate Student Fellowship, Center for Vertebrate Genomics, CornellUniversity (MVH). Whitlock KE and Westerfield M (2000).Development. 127: 3645-3653.478 Poster Developmental, Neurogenesis, and ConsumerResearchMETAMORPHOSIS OF AN OLFACTORY SYSTEM:HORMONAL REGULATION OF GROWTH ANDPATTERNING IN THE ANTENNAL IMAGINAL DISC OF THEMOTH MANDUCA SEXTAFernandez K.A. 1 , Vogt R. 1 1 Biological Sciences, University of SouthCarolina, Columbia, SCPeripheral olfactory systems of insects undergo metamorphosis,transforming from a simple larval antenna to the highly complex adultantenna mediating diverse chemosensory behaviors. Adult antennaederive from imaginal discs which grow during the larval stage, andundergo neurogenesis and morphogenesis during the pupal stage. Weare characterizing patterns of morphogenic activities in the imaginaldisc and early developing antenna to identify hormonally regulatedevents which lead to the patterning of the adult antenna.This study focuses on development the antennal disc in M. sexta.Disc growth occurs throughout most of the fifth larval instar. Theantennal imaginal disc grows inward from an epithelial ringsurrounding the base of the larval antenna. We have quantified DNAcontent during disc growth as an indicator of cell number, observing asharp decline in DNA content just prior to disc eversion. We havesubsequently identifed apoptotic activity in a spatial pattern which isreflected in the spatial organization of the adult antenna. We haveexplored the role of ecdysteroids regulating disc growth. Prior topupation the imaginal discs elongates and everts; we have demonstratedecdysteroid sensitivity of disc eversion, and are currently exploring therole of ecdysteroids in regulating the post eversion apoptotic events.These studies are establishing a foundation for identifying the hormonalregulation of growth and patterning that will give rise to the selection ofspecific chemosensory phenotypes of adult olfactory sensilla.479 Poster Developmental, Neurogenesis, and ConsumerResearchMMP-9 ELEVATION IN THE EARLY RESPONSE TOOLFACTORY NERVE INJURYCostanzo R.M. 1 , Perrino L.A. 1 , Kobayashi M. 1 1 Physiology, VirginiaCommonwealth University, Richmond, VAMatrix metalloproteinases (MMPs) have been implicated inextracellular remodeling that occurs in developmental, reparative andhomeostatic processes. MMP-9 (gelatinase B) has been reported in thecentral nervous system and may be associated with injury processes,including neuronal degeneration and gliosis. We used a welldocumentedmodel of olfactory nerve injury to study the role of MMP-9during degeneration and regeneration processes in the olfactory bulb.By means of Western blot and immunohistochemistry, we studiedMMP-9 and markers for olfactory neuron degeneration and regeneration(Olfactory marker protein, OMP and X-gal staining) and gliosis (Glialfibrillary acidic protein, GFAP) in the olfactory bulbs of P2-tau-lacZmice following bilateral olfactory nerve transection. Data from controlmice and sham surgeries showed almost no MMP-9 in the olfactorybulbs. However, we found that MMP-9 levels rose sharply and abruptly(within hours) following olfactory nerve injury and peaked at 5-7 dayspost-injury. Immunohistochemical analysis showed that MMP-9 waslocalized to the anterior portion of the olfactory bulb, the area thatsustained the greatest injury in our model. After 7 days, MMP-9 levelsdecreased, returning to near control levels at later recovery time points.This is the first report demonstrating an elevation in MMP-9 levels inthe olfactory bulb during the early response to injury, suggesting thatMMP-9 may play a role in neuronal degeneration and gliosis.Supported by NIH-NIDCD R01-DC000165.480 Poster Developmental, Neurogenesis, and ConsumerResearchSUPPORTING CELLS AND OLFACTORY NEURONSEXPRESS DIFFERENT INHIBITORY APOPTOSIS PROTEINSComte I. 1 , Carr V. 1 , Farbman A.I. 1 1 Neurobiology and Physiology,Northwestern University, Evanston, ILIn the olfactory epithelium neurogenesis and neuronal apoptosis arethought to occur continuously throughout life. We believe thatequilibrium between genesis and death of neurons is highly regulated.In this study we used RT-PCR and Northern Blot methods to examinethe expression of three members of the Inhibitory Apoptosis Proteins(IAPs) gene family in rat olfactory epithelium. These IAPs are known toinhibit apoptosis by inhibiting caspase activity and are probablyinvolved in apoptotic regulation. We established that mRNAs ofSurvivin, X-linked IAP (XIAP) and neuronal apoptosis inhibitoryprotein (NAIP) are expressed in ofactory mucosa. Cellular localizationof two proteins for which antibodies were available was studied byimmunohistochemistry whereas localization of mRNA for NAIP wasanalysed using in situ hybridization. All supporting cells are Survivinpositive,but only a subtype with a zonal distribution expresses bothXIAP and Survivin. NAIP is restricted solely to olfactory neurons.Northern blots suggested that the quantities of survivin and XIAPmRNAs did not change significantly after bulbectomy and couldexplain the low turnover of these supporting cells compared to turnoverof neurons. We have also shown by Northern blots that, NAIPexpression is down-regulated 1day after bulbectomy and up-regulated 3to 5 days post-lesion. Our data are consistent with the idea thatapoptosis is regulated in rat olfactory epithelium. Further we suggestthat apoptosis in olfactory sensory neurons and supporting cells areregulated by different molecular mechanisms. Supported by NIH grantnumber: 5R01DC4837120