Discovery and analysis of genes that govern axon guidance in the developing nervous system

神经系统功能依赖于神经元的模式化发育和突触连接的受控建立。发育中的神经元的轴突被指导性的线索引导到它们适当的目标区域，然后在那里它们选择正确的突触伙伴。这种情况发生的分子和细胞机制还不完全清楚。在这项发现资助中，我们将利用果蝇的遗传研究来了解轴突如何被这些线索引导，以及它们如何区分适当的目标和不适当的目标。这是发育神经生物学的一个中心问题，果蝇是一个理想的模型系统。尽管过去取得了成功，但果蝇的正向遗传筛选可能受到技术挑战和遗传冗余的限制，这些遗传冗余模糊了突变表型的检测。这些限制无疑留下了许多基因和分子途径有待描述。在另一种创新的方法中，我们使用了基因错误表达系统来识别可以影响轴突指导的基因和分子通路。我们最近报告了一项筛选的结果，其中我们确定了42个能够影响轴突指导的候选人，导致了从轴突子集的错误投射到严重神经系统紊乱的一系列影响。在这项发现资助中，我们的总体假设是，在我们的筛选中发现的基因的表征将揭示控制轴突指导的新分子途径。我们提出了三个主要的研究目标。首先，我们将明确识别导致观察到的错误表达表型的基因，从而发现具有轴突导向潜力的分子（目标1）。其次，我们将确定这些基因是否在发育中的神经元中表达，我们将使用体内功能丧失方法来确定这些基因是否是轴突引导所需的（目标2）。最后，我们将研究所选基因影响轴突导向的机制（目的3）。我们的总体目标是在分子水平上解释神经系统在发育过程中组织的原则，并为神经科学研究生提供世界一流的培训环境。

Nervous system function relies upon patterned development of neurons and controlled establishment of synaptic connections. Axons of developing neurons are guided by instructive cues to their appropriate target areas, where they then select their correct synaptic partners. The molecular and cellular mechanisms by which this occurs are incompletely understood. In this Discovery Grant we will use genetic studies in the fruit fly Drosophila to understand how axons are guided by these cues and how they distinguish appropriate targets from inappropriate ones. This is a central issue in developmental neurobiology, and one for which Drosophila is ideally suited as a model system. Despite past successes, forward genetic screening in Drosophila can be limited by technical challenges and by genetic redundancies that obscure the detection of mutant phenotypes. Such limitations have undoubtedly left many genes and molecular pathways remaining to be described. In an alternative and innovative approach, we have used a gene misexpression system to identify genes and molecular pathways that can influence axon guidance. We recently reported the results of a screen in which we identified 42 candidates capable of influencing axon guidance, causing a range of effects from misprojections of axon subsets to severe nervous system disorganization. In this Discovery Grant, our overall hypothesis is that characterization of genes found in our screen will reveal new molecular pathways controlling axon guidance. We propose three main research Aims. First, we will unequivocally identify the genes responsible for observed misexpression phenotypes, and thereby discover molecules with the potential to act in axon guidance (Aim 1). Second, we will determine whether these genes are expressed in developing neurons and we will use loss-of-function approaches in vivo to determine if these genes are required for axon guidance (Aim 2). Finally, we will investigate the mechanisms by which selected genes affect axon guidance (Aim 3). Our overall goal is to explain at a molecular level the principles upon which nervous systems are organized during development, and to provide a world-class training environment for graduate students in neuroscience.