During nervous system development and post-injury regeneration, nerve pathways are formed by migrating neuronal axons which are guided by extracellular cues. Although many of the major signaling pathways that regulate axon guidance have been identified, our understanding of the mechanisms by which individual genes influence specific axon guidance outcomes remains limited. In animals with complex nervous systems, such as insects and mammals, individual ligands and receptors from conserved signaling pathways can promote diverse or even opposing outcomes in different populations of neuronal axons. This proposal uses the Drosophila Robo2 receptor as a model to address the question of how individual genes can specify diverse axon guidance outcomes. Robo2 is a member of the evolutionarily conserved Roundabout (Robo) family of axon guidance receptors, and Robo2 controls at least three distinct axon guidance outcomes in the Drosophila embryonic central nervous system (CNS). The proposed research takes advantage of the molecular and genetic tools available in Drosophila to dissect the molecular and cellular mechanisms underlying the diverse axon guidance activities of Robo2. Specifically, the project will use a structure/function gene modification approach to characterize the functional domains within Robo2 that contribute to each of its axon guidance activities (Aim 1), test candidate mechanisms that may account for Robo2's uncharacterized role in promoting longitudinal pathway formation (Aim 2), and investigate how the transcriptional regulation of robo2 expression in specific neuronal populations contributes to its diverse roles in axon guidance (Aim 3). The proposed research will provide insight into how individual axon guidance genes can specify diverse developmental outcomes, identify potentially evolutionarily conserved mechanisms that may operate in other animals, including humans, where members of the Robo receptor family are also key regulators of axon guidance, and may suggest novel strategies for restoring proper regulation of axon guidance in the contexts of nervous system injury, repair, and regeneration.

Public Health Relevance

Developing therapeutic approaches to spinal cord injury and neurodegenerative diseases will require an in-depth understanding of normal nervous system development and function. The fruit fly Drosophila melanogaster is an important model for investigating the mechanisms of neural development, because many of the developmental decisions and the genes that regulate them are evolutionarily conserved in other animals, including humans. This proposal seeks to understand the mechanisms by which one such gene, known as Robo2, controls a number of different neural developmental processes in Drosophila, in hopes of providing broader insight into how evolutionarily conserved genes can control multiple aspects of neural development in Drosophila and other animals.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Academic Research Enhancement Awards (AREA) (R15)
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Special Emphasis Panel (ZRG1-MDCN-R (86)A)
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Riddle, Robert D
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University of Arkansas at Fayetteville
Schools of Arts and Sciences
United States
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