Molecular mechanisms of axon guidance and neural connectivity

7.项目摘要/摘要 这项提议侧重于定义轴突导航和连通性的分子机制。一个正常的 人类神经系统的正常运作需要数十亿个神经元的相互连接。不适当的队形或 维持这些联系会导致异常，从而导致精神疾病和精神障碍。你好吗？ 这些连接是组装和集成的吗？研究揭示了轴突的分子机制 在简单和复杂的动物之间，引导和连通性被很好地保存下来。像苍蝇这样简单的动物 使用许多与哺乳动物相同的引导信号。因此，作为了解如何 复杂的神经系统的形成和正常运作，我们一直在追求一种策略，以确定如何简单 模型苍蝇神经系统被组装-在那里我们还可以应用高分辨率的分子，遗传， 解决这一问题的生化、细胞和成像方法。事实上，我的研究计划的目标是 是专注于苍蝇胚胎简单神经系统内的一组轴突，并表征 引导它们找到目标的分子和机制。特别是，来自多个实验室的优雅研究 现在已经确定了许多引导轴突的细胞外线索和受体，揭示了基本的 轴突如何形成连接的机制。然而，对细胞内信号的了解要少得多。 将这些引导信号及其受体与轴突导航控制联系起来的途径和机制。 同样，这些引导线索要么吸引轴突，要么排斥轴突。然而，导航轴突如何选择 当它们同时遇到它们时，这些对立信号之间的关系仍远未明朗。至 回答这些问题，我们关注的是与连接有关的最大的蛋白质家族之一， 信号素(Semaphorins，SIMAs)及其丛状细胞表面受体。使用这些策略，我们的工作已经 发现了指导指导/连接的关键新分子和机制。也就是说，我们有 发现了Mical家族酶，并发现Mical和SelR酶利用特定的 控制引导/连通性的可逆生化机制。我们还发现，精确的 连接通过Semas/Plexin和包括整合素在内的其他导向分子之间的直接连接发生。 介导的黏附受体，特异性生长因子，环核苷酸，接头，小GTP酶，丝氨酸- 苏氨酸和酪氨酸激酶，以及细胞骨架的组装和分解。现在，使用这些策略， 我们的初步结果发现，这些为神经元提供连接的特定分子途径是 在空间和时间上直接由特定的分子通路指示，这些分子通路为 神经元。因此，我们假设支配神经元连接的特定因素是直接的，局部的， 由控制神经元新陈代谢的特定因素选择性地和指导性地控制。我们打算测试一下 这一具有生物医学意义的创新假说采用了严格的分子、遗传、生化、 细胞、成像方法和强大的果蝇高分辨率模型系统。

7. Project Summary/Abstract This proposal focuses on defining the molecular mechanisms of axon navigation and connectivity. A normal functioning human nervous system requires the interconnection of billions of neurons. Improper formation or maintenance of these connections leads to abnormalities that result in mental diseases and disorders. How are these connections assembled and integrated? Research has revealed that the molecular mechanisms of axon guidance and connectivity are well-conserved between simple and complex animals. Simple animals like flies use many of the same guidance signals as mammals. Therefore, as a step towards understanding how complex nervous systems form and properly function, we have pursued a strategy to determine how the simple model fly nervous system is assembled – where we can also apply high-resolution molecular, genetic, biochemical, cellular, and imaging approaches to solve this problem. Indeed, the goal of my research program is to focus on a group of axons within the simple nervous system of the fly embryo and characterize the molecules and mechanisms that guide them to their targets. In particular, elegant studies from multiple labs have now identified numerous extracellular cues and receptors that guide axons, revealing fundamental mechanisms of how axons form connections. Far less is known, however, of the intracellular signaling pathways and mechanisms that link these guidance cues and their receptors to the control of axon navigation. Likewise, these guidance cues work to either attract or repel axons. Yet, how navigating axons choose between these antagonistic signals when they simultaneously encounter them remains far from clear. To answer these questions, we have focused on one of the largest protein families involved in connectivity, the Semaphorins (Semas) and their Plexin cell-surface receptors. Employing these strategies, our work has uncovered critical new molecules and mechanisms directing guidance/connectivity. Namely, we have discovered MICAL family enzymes, and have found that MICAL and SelR enzymes employ a specific reversible biochemical mechanism to control guidance/connectivity. We have also discovered that precise connectivity occurs via direct links between Semas/Plexins and other guidance molecules including Integrin- mediated adhesive receptors, specific growth factors, cyclic nucleotides, adaptors, small GTPases, serine- threonine and tyrosine kinases, and cytoskeletal assemblers and disassemblers. Now, using these strategies, our preliminary results uncover that these specific molecular pathways that provide connectivity to neurons are spatiotemporally and directly instructed by specific molecular pathways that provide metabolic sustenance to neurons. We therefore hypothesize that specific factors that govern neuronal connectivity are directly, locally, selectively, and instructively controlled by specific factors that govern neuronal metabolism. We propose to test this biomedically significant and innovative hypothesis by employing rigorous molecular, genetic, biochemical, cellular, and imaging approaches and the robust Drosophila high-resolution model system.