Rho regulator-mediated signaling in interneuron development

描述(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能中间神经元的形态分化和功能成熟的分子机制，称为枝形吊灯细胞(CHC)。这些细胞以其独特的轴突形态为代表，具有称为盒的突起阵列， 并在维持适当的神经系统功能方面发挥核心作用。值得注意的是，CHC的形态和功能障碍在常见的大脑疾病中被发现，包括癫痫和精神分裂症。尽管这些细胞很重要，但调控CHC形态发生的分子机制在很大程度上仍不清楚。我们的研究旨在深入了解Rho调节因子在GABA能中间神经元中的作用，发现DOCK180家族成员DOCK7/Zir2在CHC的形态分化中起着关键作用。DOCK7/Zir2是RAC的激活剂。这是通过实施一种创新的方法来实现的，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DOCK7与精神分裂症相关的ErbB4酪氨酸激酶受体形成复合体，这是迄今为止唯一被证明影响CHC形态发生的另一种蛋白质。这些发现为研究CHC的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DOCK7在CHC中的作用，特别是确定DOCK7所整合的分子途径。为了实现这些目标，第一个目标将检验DOCK7表达改变不仅影响CHC的形态而且影响其生理特性的假设。具体地说，我们将通过转基因小鼠品系中GFP标记蛋白的表达来操纵大量CHC中的DOCK7水平，这将使这些细胞的电生理学研究成为可能。目的2重点研究DOCK7在CHC中的调控。我们推测DOCK7可能作为ErbB4的下游效应分子，调控CHC的形态发生和功能。我们将使用分子、生化和遗传学方法验证这一假说，并将进一步定义DOCK7调控元件，这些元件对这种相互作用和DOCK7在CHC中的功能至关重要。最后，目标3仔细研究了CHC中DOCK7下游的分子机制。我们的初步数据表明，Rac依赖和Rac非依赖的通路都参与了CHC中DOCK7‘S效应的调节。因此，我们将致力于研究RAC介导的信号转导途径，并利用创新的遗传和分子方法确定介导DOCK7功能的新的分子相互作用。拟议的研究将提供有关CHC分化和功能的分子机制的第一/重要信息。因此，他们可以为癫痫和精神分裂症等神经和精神障碍背后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.