Early mechanisms mediating the organization of the axon initial segment impact the formation of axo-axonic synapses

项目总结 大脑发育是一个复杂的过程，需要产生和分化大量的细胞和 细胞类型，以及连接的神经电路的空间和时间精度的额外挑战 这些细胞。神经回路的不正确形成导致对大脑活动模式的控制受损，并 被广泛认为是导致儿童神经性疾病的原因。多项研究表明 抑制性GABA能回路尤其有助于神经发育障碍的病理生理学-- 然而，这些疾病仍然没有得到很好的治疗。这项计划的重点是GABA能突触的形成。 在枝形吊灯细胞和称为轴突初始段(AIS)的特殊神经元之间，形成 轴突-轴突。吊灯细胞对施加分流的神经活动模式进行强大的控制 对大量主细胞组的AIS的抑制，这会影响它们产生电信号的概率 信号。轴-轴突触的特征是含有α-2亚单位和胶原蛋白的GAAA受体。 我们最近确定了特定的互动伙伴。我们已经开发了一种小鼠模型并对其进行了表征 GABAA受体α2亚单位(GABRA2-1)发生替换突变，使其与Colly的相互作用减弱。 Bistin，在发育过程中导致轴突突触数量减少和自发性癫痫发作。在……上面 在这一前提下，我们假设α2亚单位有助于人工智能的组织，以促进 轴突-轴突的形成。在这项建议中，我们将研究轴突和轴突的发育 AIS组织使用免疫组织化学和扩张显微镜，以及电路功能障碍使用 大脑皮层的记录。我们将研究这些变化如何与GABRA2-1的症状出现相关 还评估了通过使用新型光激活阳离子通道来取代失去控制的新方法 目标是AIS。与人类健康的相关性：拟议的项目预计将提供详细信息 关于AIS在发育过程中是如何组织的，以及在两种典型的AIS中轴突的形成 和病理情况，提供了关于大脑发育的基本知识和翻译见解 治疗神经发育障碍。这项提议还提供了一种积极操纵AIS的新手段，即 以其控制皮质活动模式的潜力而闻名的站点。结果：这项工作将完全进行 由UNLV的本科生和研究生组成，这是美国最多元化的校园之一。因此， 该项目将为生物医学劳动力的多样化提供有用的培训机会，如 以及改善我们机构的研究环境。

PROJECT SUMMARY Brain development is a complex process that requires the production and differentiation of numerous cells and cell types, with the additional challenge of spatial and temporal precision in the neural circuitry that connects these cells. Improper formation of neural circuitry leads to impaired control over brain activity patterns and is broadly thought to contribute to a number of childhood neurological disorders. Multiple lines of research suggest that inhibitory GABAergic circuitry in particular contributes to the pathophysiology of neurodevelopmental disor- ders, yet these disorders remain poorly treated. This project is focused on the GABAergic synapse formed be- tween a chandelier cell and a specialized neuronal compartment called the axon initial segment (AIS), forming an axo-axonic synapse. Chandelier cells exert powerful control over neural activity patterns exerting shunting inhibition at the AIS of large groups of principal cells, which impacts their probability of generating an electrical signal. Axo-axonic synapses are characterized by GABAA receptors containing the α2 subunit and collybistin, a specific interacting partner we have recently identified. We have developed and characterized a mouse model with a substitution mutation in the GABAA receptor α2 subunit (Gabra2-1) that diminishes interaction with colly- bistin, causing reduced numbers of axo-axonic synapses and spontaneous seizures during development. On this premise, we hypothesize that the α2 subunit contributes to the organization of the AIS in order to facilitate the formation of axo-axonic synapses. In this proposal we will examine axo-axonic synapse development and AIS organization using immunohistochemistry and expansion microscopy, as well as circuit dysfunction using cortical field recordings. We will examine how these changes correlate with symptom onset in the Gabra2-1 mouse and also evaluate novel methods to replace lost control by using a novel light activated cation channel targeted to the AIS. Relevance to human health: The proposed project is expected to yield detailed information about how the AIS organizes during development, as well as the formation of axo-axonic synapses in both typical and pathological conditions, providing both basic knowledge about brain development and translational insights for neurodevelopmental disorders. This proposal also offers a novel means of actively manipulating the AIS, a site known for its potential to control cortical activity patterns. Outcomes: This work will be conducted entirely by undergraduate and graduate students at UNLV, which is one of the nation’s most diverse campuses. Thus, this project will provide instrumental training opportunities for the diversification of the biomedical workforce, as well as enhance the research environment of our institution.