Molecular mechanisms underlying cortical interneuron synaptic specificity

项目摘要/摘要 皮质抑制性GABA能中间神经元(INS)形成复杂的局部回路，对高级中枢神经系统起关键调节作用。 通过平衡和塑造神经元活动来调整大脑功能。与它在以下方面不可或缺的作用相一致 大脑功能正常，抑制系统的畸形/故障牵涉到广泛的大脑 精神分裂症、自闭症和癫痫等疾病。尽管它们很重要，但分子机制 在IN局部电路的布线下面仍然很大程度上是未知的。皮质INS由不同类型的细胞组成 由形态、生理和基因表达来定义。值得注意的是，不同的IN亚型也显示出不同的 突触在板层/细胞和亚细胞水平的特异性。尽管亚型特异性突触 连接性被认为是INS的关键属性，以确保抑制系统的功能多样性， 突触特异性的分子机制尚不清楚。这样做的目的是 建议确定IN亚型建立层/细胞型的分子机制- 以及亚细胞区特异性突触。为了实现这一目标，我们将进行一系列实验 使用枝形吊灯细胞(CHC)，它专门支配层特定的轴突起始节段(AISS) 锥体神经元(PNS)。众所周知，CHC对Pn峰的产生起着关键的调节作用，并已被牵连 精神分裂症和癫痫。除了它们的功能意义外，它们突触的刻板印象 组织使CHCs成为研究IN突触特异性分子机制的一个有吸引力的模型。 我们的初步数据表明：(1)已知相互结合的IgSF11蛋白得到了表达 在CHC和层特异性靶PNS中，(2)已知与AIS富含的蛋白结合的GLDN蛋白， NF186在CHCs中优先表达，(3)CHCs中的IgSF11在其突触前反应中起重要作用 发育，(4)GLDN和NF186似乎在启动CHC突触中发挥作用，以及(5)游离的IgSF11 GLDN-NF186系统似乎不能诱导CHC突触。基于我们的发现，我们建议测试 假设层特异性突触发生作用和亚细胞区特异性识别 分别通过IgSF11亲和性相互作用和GLDN-NF186相互作用协同介导 测定CHC突触的特异性。我们将追求以下具体目标来检验我们的假设。在目标1中， 我们将确定突触前和突触后神经元之间的IgSF11同源相互作用在 CHC形成的层特异性突触。在目标2中，我们将确定GLDN和NF186在CHC中的作用 在AISS上形成突触。在目标3中，我们将确定NF186/GLDN在门控IgSF11中的调节作用 在AISS诱发CHC突触前循环的信号。在这项研究完成后，我们不仅将获得 对IN连接的分子机制的重要见解也是开发治疗策略的线索 从功能上修复紊乱/受损的大脑。

Project Summary/Abstract Cortical inhibitory GABAergic interneurons (INs), which develop intricate local circuits, critically regulate higher- order brain functions by balancing and shaping neuronal activity. Consistent with its indispensable role in normal brain functions, malformation/malfunction of the inhibitory system is implicated in a wide array of brain disorders such as schizophrenia, autism, and epilepsy. Despite their importance, the molecular mechanisms underlying the wiring of IN local circuits remain largely unknown. Cortical INs comprise diverse cell types that are defined by morphology, physiology, and gene expression. Notably, different IN subtypes also show distinct synaptic specificity at laminar/cellular as well as subcellular levels. Although subtype-specific synaptic connectivity is considered a critical property of INs to ensure functional diversity of the inhibitory system, the molecular mechanisms underlying IN synaptic specificity remains poorly understood. The objective of this proposal is to determine the molecular mechanisms by which IN subtypes establish layer/cell type- and subcellular domain-specific synapses. To achieve this goal, we will perform a series of experiments using chandelier cells (ChCs), which exclusively innervate axon initial segments (AISs) of layer-specific pyramidal neurons (PNs). The ChC is known to critically regulate PN spike generation and has been implicated in schizophrenia and epilepsy. Besides their functional significance, the stereotypy of their synaptic organization make ChCs an attractive model to study the molecular mechanisms for IN synaptic specificity. Our preliminary data has shown that: (1) IgSF11 proteins that are known to bind with each other are expressed in both ChCs and layer-specific target PNs, (2) Gldn proteins that are known to bind to AIS-enriched proteins, NF186, are preferentially expressed in ChCs, (3) IgSF11 in ChCs plays an essential role in their presynaptic development, (4) Gldn and NF186 appear to play a role in initiating ChC synapses, and (5) IgSF11 that is free from the Gldn-NF186 system appears not to induce ChC synapses. Based on our findings, we propose to test the hypothesis that the layer-specific synaptogenic action and the subcellular domain-specific recognition mediated through IgSF11 homophilic interactions and Gldn-NF186 interactions, respectively, cooperatively determine ChC synaptic specificity. We will pursue the following specific aims to test our hypothesis. In Aim 1, we will determine the role of the IgSF11 homophilic interaction between pre- and postsynaptic neurons in layer-specific synapse formation by ChCs. In Aim 2, we will determine the role of Gldn and NF186 in ChC synapse formation on AISs. In Aim 3, we will determine the regulatory role of NF186/Gldn in gating IgSF11 signaling to induce ChC presynaptic boutons at AISs. Upon completion of this study, we will gain not only important insights into molecular mechanisms for IN wiring but also a clue to developing therapeutic strategies to functionally repair disordered/damaged brains.