Development and Function of Mammalian Chemosensory Systems

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The research goals of the Section of Molecular Neurobiology are to define the molecular mechanisms underlying the development and function of mammalian chemosensory systems. One area of emphasis is the identification of molecules that direct the establishment of the precise patterns of synaptic connectivity observed between peripheral olfactory sensory neurons and their target neurons in the olfactory bulb. Previous studies led to the identification of the sema4g gene that encodes a novel axonal guidance molecule highly expressed in chemosensory neurons of the developing olfactory and vomeronasal systems. Results obtained during the past year indicate that other members of the sema family, based on their early developmental expression patterns in sensory neurons, may act in concert with Sema4g to mediate axonal targeting. There is very little known about the cellular and molecular mechanisms critical for taste perception. During the past year, studies aimed at identifying molecules important for gustatory system function were initiated. In an attempt to identify novel genes expressed in taste buds where the initial step of gustatory information processing occurs, the expression patterns of over 200 novel EST clones derived from a rat taste tissue cDNA library were examined by in situ hybridization. Several expression profiles were observed among the genes analyzed including genes abundantly expressed in all taste buds as well as genes whose expression was limited to a subset of taste buds. Such genes will provide much needed taste bud specific markers for future developmental and functional studies. In addition, RT-PCR based approaches and database analysis have identified candidate genes, currently under study, that may encode components of the gustatory signal transduction machinery.