IgSF protein interactions drive specificity in circuit wiring and synaptic elaboration

项目摘要 在这个应用中，我们研究了指导神经连接和轴突终末的分子机制。 详述。我们关注果蝇的神经肌肉系统，因为它的连通性不变，有限 突触伙伴和可访问性。考虑到这种“简单”的电路已经被研究了40多年，它是 有些令人惊讶的是，关于运动神经元如何选择适当的 肌肉靶点以及每个运动神经元如何发展出独特的、但定型的轴突终末结构， 是突触功能的基础。从概念上讲，这两个发育过程都依赖于特异性线索 指导突触伙伴匹配(角色1)和每个轴突终末的突触精化(角色2)。为了支持…… 第一个角色，我们之前发现了两个相互作用的细胞表面蛋白(CSP)，DIP-α和Dpr10，它们是 将运动神经元连接到肌肉的一个子集所必需的。为了支持第二个角色，这些CSP继续 在连接之后表达，暗示在突触发育中有额外的功能。我们的中央 假设DPR-DIP的组合相互作用，除了指定突触连接外，还 参与确定特定突触的结构和功能。对电路开发的洞察 在之前的一次合作中，我们描述了DPR-OME，即两个人之间的一组互动 免疫球蛋白超家族中的DPRs和DIPs。这32种蛋白质在体内相互结合 独特的组合，我们的初步数据揭示了果蝇幼虫独特的表达模式 神经肌肉回路。此外，我们的数据支持组合DPR-DIP交互模型，该模型利用 顺式/反式相互作用，指导高度特异的突触伙伴关系。我们还揭示了一条新的信号通路 这是局部突触阐述的基础。考虑到我们的发现和基因试剂，我们处于一个独特的位置 不仅是为了比较轴突分支特定的识别标记，而且还为了询问突触是否详述 邻近的轴突终末可以独立调节。在第一个目标中，我们利用DPR-OME和 6个DIPs在多神经运动神经元中的表达以执行单细胞遗传操作和 研究组合DPR-DIP代码如何指示连接性。此外，我们生成的亲和力变体 揭示一个协调的顺式/反式相互作用模型，以增强特异性。在第二个目标中，我们利用 功能和遗传方法，以了解共同神经输入如何发展独特的形态和 功能属性。我们发现了一种新的轴突之间的串扰信号通路，它局部地雕刻 NMJ尺寸。总体而言，这些研究将揭示神经回路所需的基本发育程序 连线和轴突终末的阐述，重点是CSP代码如何调制这些过程中的每一个。

Project Summary In this application, we examine the molecular mechanisms that instruct neural wiring and axon terminal elaboration. We focus on the Drosophila neuromuscular system due to its invariant connectivity, limited synaptic partners, and accessibility. Given that this ‘simple’ circuit has been studied for over four decades, it is somewhat surprising that fundamental questions still exist as to how motor neurons choose their appropriate muscle targets and how each motor neuron develops a unique, yet stereotyped, axon terminal structure that underlies synaptic function. Conceptually, both of these developmental processes rely on specificity cues to guide synaptic partner matching (role 1) and synaptic elaboration at each axon terminal (role 2). In support of the first role, we previously discovered two interacting cell surface proteins (CSPs), DIP-α and Dpr10, that are required for wiring a motor neuron to a subset of muscles. In support of the second role, these CSPs continue to be expressed after connectivity, implying additional functions in synaptic development. Our central hypothesis is that combinatorial Dpr-DIP interactions, in addition to specifying synaptic connections, also participate in determining the structure and function of specified synapses. Insights into circuit development arose in a prior collaboration where we characterized the ‘Dpr-ome’, the set of interactions between two families of the immunoglobulin superfamily, the Dprs and DIPs. These 32 proteins bind to one another in unique combinations, and our preliminary data reveal unique expression patterns in the Drosophila larval neuromuscular circuit. Additionally, our data support a combinatorial Dpr-DIP interaction model that leverages cis/trans interactions to instruct highly specific synaptic partnerships. We also reveal a novel signaling pathway that underlies local synaptic elaboration. Given our findings and genetic reagents, we are in a unique position not only to compare axon branch-specific identification tags but also to ask if synaptic elaboration of neighboring axon terminals can be independently regulated. In the first aim, we capitalize on the Dpr-ome and the expression of 6 DIPs in multi-innervating motor neurons to perform single-cell genetic manipulations and examine how combinatorial Dpr-DIP codes instruct connectivity. In addition, we generate affinity variants to reveal a coordinated cis/trans interaction model that enhances specificity. In the second aim, we utilize functional and genetic approaches to understand how co-innervating inputs develop unique morphological and functional properties. We identify a novel crosstalk signaling pathway between axon arbors that locally sculpts NMJ size. Overall, these studies will uncover fundamental developmental programs required for neural circuit wiring and axon terminal elaboration, with emphasis on how CSP codes modulate each of these processes.