DOCK7 Signaling in Neuronal Development

描述（由申请人提供）：本申请的长期目标是了解控制出生后哺乳动物前脑中神经元前体（神经母细胞）迁移的分子和细胞机制。这些前体在前脑室下区（SVZ）产生，然后通过吻侧迁移流（RMS）迁移到嗅球（OB），在那里它们加入现有的回路并分化成中间神经元。新生成的神经母细胞向OB的适当迁移和整合对于嗅觉学习和可塑性非常重要，值得注意的是，这些过程的缺陷与异常的先天和社会行为有关。重要的是，神经母细胞也能够迁移到脑损伤部位，这增加了它们在脑治疗中应用的可能性。尽管神经母细胞迁移的重要性，但对调节这一过程的分子机制知之甚少。我们最近发现DOCK180家族成员DOCK7是Rac的激活因子，在出生后/成年小鼠前脑的神经母细胞中显著表达，重要的是它在RMS的神经母细胞迁移中起关键作用。此外，我们发现DOCK7与精神分裂症相关的ErbB4酪氨酸激酶受体相互作用，显著影响RMS神经母细胞迁移。这些发现为研究出生后前脑神经母细胞迁移的分子基础提供了一个独特的切入点。本应用旨在进一步确定DOCK7在迁移神经母细胞中的作用，并确定DOCK7不可或缺的分子途径。为了实现这些目标，Aim 1将通过遗传和活细胞成像实验进一步研究DOCK7缺失对神经母细胞迁移行为的影响。我们还将利用CreER转基因小鼠模型和诱导RNAi技术，确定DOCK7缺失神经母细胞的后续命运。目的2将研究DOCK7在神经母细胞迁移中的调节机制，特别关注ErbB4，我们假设ErbB4是DOCK7在神经母细胞迁移中的关键调节因子。我们将使用分子、遗传和生化方法来验证这一假设，并将进一步定义DOCK7在神经母细胞中相互作用和DOCK7功能的重要调控元件。最后，Aim 3将描述DOCK7在迁移神经母细胞中的下游分子机制。我们的初步数据表明，DOCK7通过rac依赖性和rac非依赖性途径发挥其作用，每种途径都影响神经母细胞迁移的不同细胞方面。因此，我们将利用创新的遗传、分子和细胞方法，努力描绘rac介导的信号通路，并确定介导DOCK7对神经母细胞迁移影响的新分子相互作用。提出的研究将为控制出生后神经母细胞迁移的机制提供新的见解。因此，它们应该揭示嗅觉缺陷和相关中枢神经系统疾病背后的信号缺陷，并有助于开发治疗脑损伤的新治疗策略。

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.