Semaphorin4D and PlexinB1 mediate GABAergic synapse development in mammalian CNS

描述（由申请人提供）：脑信号蛋白4D和丛蛋白B1介导哺乳动物CNS中GABA能突触发育。正确的神经元通讯依赖于神经元之间突触连接的精确组装和发展。许多神经障碍由突触连接的扰动引起，例如精神发育迟滞、自闭症和Rett综合征（费尔南德斯和Garner，2007; Rubenstein和Marzenich，2003; Tabuchi等人，2007; Zoghbi，2003）。此外，许多突触蛋白，包括脑信号蛋白家族成员，已经与神经发育障碍有关（韦斯等人，2009），并且脑信号蛋白的缺乏导致啮齿动物中不适当的突触连接（Morita等人，2006;奥康纳等人，2009;帕拉迪斯等人，2007; Sahay等人，2005年）。的 跨膜蛋白Sema 4D对于适当的GABA能突触形成是必需的，因为通过RNAi敲低突触后神经元中的表达导致培养的神经元中GABA能突触密度的降低（帕拉迪斯et al 2007）。我们的初步结果表明，除了可溶性，Sema 4D的细胞外结构域培养的海马神经元足以驱动GABA能突触的形成。重要的是，这种增加依赖于Sema 4D受体PlexinB 1的表达。此外，我们的电压钳实验表明，丛蛋白B1是必要的适当的GABA能突触传递在海马。因此，我们的工作定义丛蛋白B1作为一种新的受体介导GABA能突触的形成，在哺乳动物中枢神经系统中的Sema 4D。本研究的目的是阐明Sema 4D及其受体丛蛋白B1在GABA能突触发育中的作用。在这里提出的实验中，我们假设Sema 4D通过其受体丛蛋白B1启动GABA能突触蛋白如GABAA受体和桥蛋白的组装。这将在培养的海马神经元中使用多种成像技术进行测试，包括共聚焦和延时成像，以测量用可溶性Sema 4D处理后神经元中GABA能突触蛋白的迁移率和积累。此外，初步数据表明，丛蛋白B1是重要的GABA能突触传递。电生理学将用于确定丛蛋白B1调节GABA能突触传递功能的作用部位。这里提出的实验不仅将大大扩展我们对GABA能突触发育中一种新的受体-配体对的理解，它还将告知我们GABA能突触发生的一些基本机制。!

DESCRIPTION (provided by applicant): Semaphorin4D and PlexinB1 mediate GABAergic synapse development in mammalian CNS. Proper neuronal communication depends on the precise assembly and development of synaptic connections between neurons. Many neurological disorders arise from perturbations in synaptic connectivity, such as mental retardation, autism, and Rett Syndrome (Fernandez and Garner, 2007; Rubenstein and Marzenich, 2003; Tabuchi et al., 2007; Zoghbi, 2003). In addition, many synaptic proteins, including Semaphorin family members, have been linked to neurodevelopmental disorders (Weiss et al, 2009) and the lack of Semaphorins results in improper synaptic connectivity in rodents (Morita et al., 2006; O'Connor et al., 2009; Paradis et al., 2007; Sahay et al., 2005). The transmembrane protein Sema4D is necessary for proper GABAergic synapse formation, as knockdown of expression in the postsynaptic neuron by RNAi leads to a decrease in GABAergic synaptic density in cultured neurons (Paradis et al 2007). Our preliminary results demonstrate that addition of the soluble, extracellular domain of Sema4D to cultured hippocampal neurons is sufficient to drive GABAergic synapse formation. Importantly, this increase is dependent on the expression of Sema4D's receptor, PlexinB1. In addition, our voltage-clamp experiments indicate that PlexinB1 is necessary for proper GABAergic synaptic transmission in the hippocampus. Thus, our work defines PlexinB1 as a novel receptor mediating GABAergic synapse formation in response to Sema4D in the mammalian CNS. The goal of this proposal is to elucidate the role of Sema4D and it's receptor, PlexinB1 in GABAergic synapse development. In experiments proposed here, we hypothesize that Sema4D acts to initiate assembly of GABAergic synaptic proteins such as GABAA receptors and gephyrin through its receptor PlexinB1. This will be tested using a variety of imaging techniques in cultured hippocampal neurons, including confocal and time- lapse imaging, to measure the mobility and accumulation of GABAergic synaptic proteins in neurons after treatment with soluble Sema4D. In addition, preliminary data suggests that PlexinB1 is important for GABAergic synaptic transmission. Electrophysiology will be used to determine the site of action of PlexinB1 function to regulate GABAergic synaptic transmission. The experiments proposed here will not only greatly expand our understanding of a novel receptor-ligand pair in GABAergic synapse development; it will inform us as to some of the basic mechanisms underlying GABAergic synaptogenesis. !