Rho regulator-mediated signaling in interneuron development

描述（由申请人提供）：本申请的长期目标是确定控制一类独特的抑制性GABA能中间神经元（称为枝形细胞（ChC））的形态分化和功能成熟的分子机制。这些细胞的典型特征是它们独特的轴突形态，具有称为盒的终扣阵列， 并在维持正常的神经系统功能中发挥核心作用。值得注意的是，ChC形态和功能扰动发现在常见的大脑疾病，包括癫痫和精神分裂症。尽管这些细胞的重要性，调节ChC形态发生的分子机制仍然在很大程度上未知。我们的研究旨在深入了解Rho调节剂在GABA能中间神经元中的作用，揭示了DOCK 180家族成员DOCK 7/Zir 2（Rac的激活剂）在ChCs形态分化中的关键作用。这是通过实施一种创新方法实现的，该方法能够在发育中的小鼠胚胎中原位对单个ChC进行遗传标记和操作。此外，我们最近发现DOCK 7与精神分裂症相关的ErbB 4酪氨酸激酶受体形成复合物，值得注意的是，迄今为止唯一的其他蛋白质被证明会影响ChC形态发生。这些发现为研究ChC形态发生和功能的分子基础提供了一个独特的切入点。本申请旨在进一步确定DOCK 7在ChC中的作用，特别是鉴定DOCK 7所整合的分子途径。为了实现这些目标，第一个目标将测试的假设，改变DOCK 7的表达不仅影响的形态，但也ChCs的生理特性。具体地说，我们将操纵DOCK 7水平在一个大的群体的ChCs可视化通过GFP标记蛋白表达在一个遗传修饰的小鼠系，这将允许这些细胞的电生理学研究。目的2集中于ChCs中DOCK 7的调节。我们推测DOCK 7作为ErbB 4的下游效应子来控制ChC的形态发生和功能。我们将使用分子，生物化学和遗传学的方法来测试这一假设，并将进一步定义这种相互作用和DOCK 7在ChCs中的功能的重要DOCK 7调控元件。最后，目的3详细研究了ChCs中DOCK 7下游的分子机制。我们的初步数据表明Rac依赖性和Rac非依赖性途径都参与介导DOCK 7在ChCs中的作用。因此，我们将努力表征所涉及的Rac介导的信号通路，并使用创新的遗传和分子方法鉴定介导DOCK 7功能的新型分子相互作用。拟议的研究将提供第一个/重要的信息，控制ChC分化和功能的分子机制。因此，它们可以为神经和精神疾病（如癫痫和精神分裂症）的信号缺陷提供新的线索。

DESCRIPTION (provided by applicant): The long-term goal of this application is to define the molecular mechanisms that govern the morphological differentiation and functional maturation of a unique class of inhibitory GABAergic interneurons, called chandelier cells (ChCs). These cells are typified by their distinctive axonal morphology with arrays of boutons termed cartridges, and play a central role in maintaining proper nervous system function. Significantly, ChC morphological and functional perturbations are found in common brain disorders, including epilepsy and schizophrenia. Despite the importance of these cells, the molecular mechanisms that regulate ChC morphogenesis remain largely unknown. Our studies initiated to gain insight into the role of Rho regulators in GABAergic interneurons revealed a critical role for the DOCK180 family member DOCK7/Zir2, an activator of Rac, in the morphological differentiation of ChCs. This was made possible by implementing an innovative method that enables genetic labeling and manipulation of single ChCs in situ in developing mouse embryos. Furthermore, we recently found that DOCK7 forms a complex with the schizophrenia-linked ErbB4 tyrosine kinase receptor, which notably the only other protein is so far shown to affect ChC morphogenesis. These findings provide a unique entry point for studies of the molecular basis of ChC morphogenesis and function. This application aims to further define the role of DOCK7 in ChCs, and in particular to identify the molecular pathways DOCK7 is integral to. Towards these goals, the first aim will test the hypothesis that altered DOCK7 expression impacts not only the morphology but also the physiological properties of ChCs. Specifically, we will manipulate DOCK7 levels in a large population of ChCs visualized via GFP marker protein expression in a genetically modified mouse line, which will permit electrophysiology studies of these cells. Aim 2 focuses on the regulation of DOCK7 in ChCs. We conjecture that DOCK7 acts as downstream effectors of ErbB4 to control ChC morphogenesis and function. We will test this hypothesis using molecular, biochemical and genetic approaches and will further define DOCK7 regulatory elements important for this interaction and for DOCK7 function in ChCs. Finally, aim 3 scrutinizes molecular mechanisms downstream of DOCK7 in ChCs. Our preliminary data imply that both Rac-dependent and Rac-independent pathways are involved in mediating DOCK7's effects in ChCs. Hence, we will strive to characterize the Rac-mediated signaling pathways involved and identify novel molecular interactions that mediate DOCK7 function using innovative genetic and molecular approaches. The proposed studies will provide first/vital information on the molecular mechanisms governing ChC differentiation and function. As such, they could shed novel light onto the signaling defects that underlie neurological and mental disorders, such as epilepsy and schizophrenia.