Olfactory sensory neuron (OSN) genesis is an ongoing process that begins early in development and continues in adults. It requires that newly generated axons successfully navigate through the lamina propria and the cribiform plate, into the central nervous system. Disruptions in neurodevelopmental events are responsible for a wide range of diseases, including Autism, Fragile X, Lissencephaly, and Kallman's syndrome. My ultimate goal is to improve our understanding of the mechanisms that drive and regulate axonal outgrowth. Specifically, my goal in this proposal is to study the development of the olfactory pathway and test the hypothesis that Dishevelled (Dvl) proteins influence both axon guidance and synapse formation. Axon guidance cues, cell adhesion molecules, and odor receptor induced activity have all been implicated in the precise final targeting of OSN axons to specific glomeruli. However, the mechanisms used by OSN axons to extend an axon from the olfactory epithelium (OE) toward the olfactory bulb (OB) are only partially understood, and often controversial. Similarly, the molecules involved in establishing the synapses between the OSNs and the projection neurons in the OB are not well understood. Wnt secreted molecules, acting through Frizzled (Fz) receptors are implicated in many processes, including axon guidance and synapse formation. We recently found several of these molecules in the olfactory system, in a pattern suggestive of a role in OSN axon outgrowth. One key molecule in the signaling pathway after Fz activation is Dvl. This proposal includes a systematic characterization of the expression patterns of all three Dvl (Dvl-1, -2 and -3) molecules and some candidate downstream signaling molecules (e.g. RhoA, Daam-1, ROCK) in the olfactory system. Both protein (Western blot and immunohistochemistry), and mRNA (RT-PCR and in situ hybridization) expressions will be studied. The role of Dvl molecules will be assessed by injecting a characterized silencing RNA (siRNA) by in utero electroporation, which I recently optimized to label OSNs in the OE. The results from this proposal will promote our understanding of the role of the Wnt-Fz signaling pathways, including Dvls, in OSN axons. This, in turn, will have a significant impact on understanding axon guidance and synapse formation in the olfactory system, and broadly in other regions of the central nervous system.

Public Health Relevance

Loss of the sense of smell is an early indicator of several major neurological diseases in humans including Alzheimer's disease, Parkinson's disease, and schizophrenia. As new neurons mature in the olfactory epithelium in the nasal cavity, they extend an axon that navigates long distances into the central nervous system. This project proposes understanding the mechanisms used by olfactory sensory neuron axons to grow into the olfactory bulb, which will give us the knowledge to manipulate them and use them in therapeutic strategies for neurodegenerative diseases, and perhaps provide new insights into the etiology of diseases such as Kallman's syndrome in which the olfactory system fails to properly develop.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Small Research Grants (R03)
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Special Emphasis Panel (ZDC1-SRB-R (37))
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Sullivan, Susan L
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Yale University
Schools of Medicine
New Haven
United States
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Rodriguez-Gil, Diego J; Bartel, Dianna L; Jaspers, Austin W et al. (2015) Odorant receptors regulate the final glomerular coalescence of olfactory sensory neuron axons. Proc Natl Acad Sci U S A 112:5821-6
Mobley, Arie S; Rodriguez-Gil, Diego J; Imamura, Fumiaki et al. (2014) Aging in the olfactory system. Trends Neurosci 37:77-84
Rodriguez-Gil, Diego J; Hu, Wilbur; Greer, Charles A (2013) Dishevelled proteins are associated with olfactory sensory neuron presynaptic terminals. PLoS One 8:e56561