A role for ephrins-A2, -A3, & -A5 in excitatory synaptic development and function

描述（由申请人提供）：复杂的思想和运动需要整合有关感觉、运动和动机状态的地形组织的皮层信息。这些整合的网络涉及中棘投射神经元（MSN）的树突棘上的皮质纹状体突触，其被组织成纹状体内的独特隔室。表观遗传和遗传因素，改变调节纹状体神经元室，皮质纹状体传入组织，或突触生理学的正常发展的分子的表达可能参与与纹状体相关的神经精神疾病的病因。因此，我的建议的目的是确定一个分子家族的细胞表面信号分子，A类肝配蛋白的成员，在纹状体电路的正常发展的作用。Eph/ephrins是一种引人注目的候选分子，由于其调节神经元迁移、轴突通路拓扑和树突形态以及通过谷氨酸受体运输调节突触功能的能力，它们可能参与调节纹状体区室和皮质纹状体突触发生的适当形成所必需的发育事件。肝配蛋白-A2、-A3和-A5基因缺失的小鼠具有混乱的纹状体亚区室，并且在运动活动水平、重复的面部修饰和在学习期间坚持不适当的运动策略方面显示差异。这些观察结果表明，某些A-肝配蛋白可以不同地影响与皮质纹状体功能相关的正常行为所必需的解剖学和生理学特征。目前尚不清楚ephrin-A2，-A3和/或-A5的相对表达的变化是否会影响皮质纹状体突触的突触发育或神经传递。因此，本研究将包括电生理学研究，以检查谷氨酸受体贩运的变化和形态学的体视学研究，以测量纹状体中的主要投射神经元--中棘神经元（MSN）树突的变化。MSN的两种亚型通过多巴胺受体D1或D2表达来区分，并且这些亚型分别形成“直接”和“间接”基底神经节通路。由于许多与纹状体功能障碍相关的神经精神疾病被认为涉及这两种途径之间的功能失衡，因此特别感兴趣的是了解A-肝配蛋白相对比例的变化可能对这两种MSN人群的兴奋性生理学产生的影响。该建议需要使用在每个MSN亚型中表达荧光标记蛋白的独特转基因小鼠，并结合肝配蛋白-A2、-A3和/或-A5的遗传缺失。该模型允许评估D1+与D2+ MSN中的谷氨酸受体活性和树突状形态。指导性假设是，Ephrin-A2/3/5特异性缺失的小鼠的D1+与D2+ MSNs中，神经元能突触传递和树突形态的变化将发生差异。因此，这些研究将评估可能在多个层面上导致发育性神经精神障碍病因学的遗传因素。 公共卫生相关性：复杂的思想和运动需要整合皮质信息的感觉，运动和动机状态的兴奋性突触纹状体中型棘神经元（MSN）。几种以异常重复性思维或行为为特征的神经精神疾病与表达D1或D2多巴胺受体的MSN投射的相对活性的功能失衡有关。这些研究将探讨如何在特定成员的A-ephrin类信号分子的遗传缺失有助于解剖和功能异常的皮质纹状体突触对D1+与D2+ MSN，增加了解的分子因素，影响这些电路的发展，以及他们的作用，神经精神疾病的病因。

DESCRIPTION (provided by applicant): Complex thoughts and movements require the integration of topographically organized cortical information about sensory, motor, and motivational states. These integrated networks involve corticostriatal synapses on dendritic spines of medium spiny projection neurons (MSNs), which are organized into unique compartments within the striatum. Epigenetic and genetic factors that alter the expression of molecules regulating the normal development of striatal neuronal compartments, corticostriatal afferent organization, or synaptic physiology could be involved in the etiology of the neuropsychiatric disorders associated with the striatum. Thus, my proposal aims are to identify a role for members of one molecular family of cell-surface signaling molecules, the A-class ephrins, in the proper development of striatal circuitry. Eph/ephrins are compelling candidate molecules that could participate in developmental events necessary to regulate the proper formation of striatal compartments and corticostriatal synaptogenesis due to their ability to regulate neuronal migration, axonal pathway topography and dendritic morphology, as well as modulate synaptic function via glutamate receptor trafficking. Mice with genetic deletions of ephrins-A2, -A3, and -A5 have disorganized striatal sub compartments and display differences in locomotor activity levels, repetitive facial grooming, and perseverance of inappropriate motor strategies during learning. These observations suggest that certain A- ephrins could differentially affect anatomical and physiological features essential for normal behaviors associated with corticostriatal function. It is currently unknown whether changes in the relative expression of ephrin-A2, -A3, and/or -A5 affect synaptic development or neurotransmission at corticostriatal synapses. Therefore, this research will include electrophysiology studies to examine changes in glutamate receptor trafficking and stereological studies of morphology to measure changes in dendrites of medium spiny neurons (MSNs), the main projection neurons in the striatum. Two subtypes of MSNs are distinguished by dopamine receptor D1 or D2 expression and these form the "direct" and "indirect" basal ganglia pathways, respectively. As many neuropsychiatric disorders linked to striatal dysfunction are thought to involve a functional imbalance between these two pathways, it is of particular interest to understand the effect that changes in the relative proportion of A-ephrins might have on excitatory physiology in these two populations of MSNs. This proposal entails use of unique transgenic mice expressing fluorescent marker proteins in each MSN subtype in combination with genetic deletions of ephrins-A2, -A3, and/or -A5. This model permits assessment of glutamate receptor activity and dendritic morphology in D1+ vs. D2+ MSNs. The guiding hypothesis is that changes in glutamatergic synaptic transmission and dendritic morphology will occur differentially in D1+ versus D2+ MSNs of mice with specific deletions of ephrins-A2/3/5. These studies will thus evaluate genetic factors that could contribute at multiple levels to the etiology of developmental neuropsychiatric disorders. PUBLIC HEALTH RELEVANCE: Complex thoughts and movements require the integration of cortical information about sensory, motor, and motivational states at excitatory synapses on striatal medium spiny neurons (MSNs). Several neuropsychiatric disorders that are characterized by abnormal repetitive thoughts or behaviors have been linked to a functional imbalance in the relative activity of projections from MSNs expressing either D1 or D2 dopamine receptors. These studies will investigate how genetic deletions in specific members of the A-ephrin class of signaling molecules contribute to anatomical and functional abnormalities at corticostriatal synapses on D1+ versus D2+ MSNs, to increase understanding of the molecular factors that influence the development of these circuits as well as their role in the etiology of neuropsychiatric disorders.