DOCK7 Signaling in Neuronal Development

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DESCRIPTION (provided by applicant): The long-term goal of this application is to understand the molecular and cellular mechanisms that govern the migration of neuronal precursors (neuroblasts) in the postnatal mammalian forebrain. These precursors are generated in the forebrain subventricular zone (SVZ) and then migrate via the rostral migratory stream (RMS) to the olfactory bulb (OB) where they join existing circuitries and differentiate into interneurons. Proper migration and integration of newly generated neuroblasts into the OB is important for olfactory learning and plasticity, and, significantly, deficiencies in these processes have been linked to abnormal innate and social behavior. Importantly, neuroblasts are also capable of migrating to sites of injury in the brain, raising the possibility for their use in brain therapies Despite the importance of neuroblast migration, little is known about the molecular mechanisms that regulate this process. We recently uncovered that the DOCK180 family member DOCK7, an activator of Rac, is prominently expressed in neuroblasts in the forebrain of postnatal/adult mice, and importantly that it plays a critical role in neuroblast migration in the RMS. Furthermore, we found that DOCK7 interacts with the schizophrenia-associated ErbB4 tyrosine kinase receptor, which notably was shown to influence RMS neuroblast migration. These findings provide a unique entry point for studying the molecular basis of neuroblast migration in the postnatal forebrain. This application aims to further define DOCK7's role in migrating neuroblasts and identify the molecular pathways DOCK7 is integral to. Towards these goals, Aim 1 will further scrutinize the effects of DOCK7 depletion on the migratory behavior of neuroblasts by performing genetic and live cell imaging experiments. We will also determine the ensuing fate of DOCK7 depleted neuroblasts, taking advantage of a CreER transgenic mouse model and inducible RNAi technology. Aim 2 will investigate mechanisms of DOCK7 regulation in migrating neuroblasts, with a particular focus on ErbB4, which we postulate is a key regulator of DOCK7 in neuroblast migration. We will test this hypothesis using molecular, genetic and biochemical approaches and will further define DOCK7 regulatory elements important for this interaction and DOCK7 function in neuroblasts. Finally, Aim 3 will characterize molecular mechanisms downstream of DOCK7 in migrating neuroblasts. Our preliminary data suggest that DOCK7 exerts its effects via both Rac-dependent and Rac-independent pathways, each influencing distinct cellular aspects of neuroblast migration. Hence, we will strive to delineate te Rac-mediated signaling pathway(s) involved and identify novel molecular interactions that mediate DOCK7's effects on neuroblast migration, using innovative genetic, molecular and cellular approaches. The proposed studies will provide novel insights into the mechanisms governing postnatal neuroblast migration. As such, they should shed light onto the signaling defects that underlie olfactory deficits and associated CNS disorders, and could aid in the development of novel therapeutic strategies to treat brain injury.