Molecular Mechanisms of Axon Branching in Synaptic Development

描述(申请人提供)：轴突分支允许神经元与多个伙伴通信，并有助于建立形态和功能上不同的神经网络。为了确保正确的突触连接，分支受到信号通路的严格调控，这些信号通路允许环境线索指示轴突何时何地进行分支。这项拟议研究的长期目标是研究这一调控的分子和细胞基础，了解它如何在突触连接的初始发育和随后的可塑性重排中发挥作用，并为如何在损伤后再生新的分支和功能连接提供见解。以背根神经节和三叉神经节的啮齿动物感觉神经元典型轴突分支的发育为模型，我们发现了一条涉及分泌分子缝隙促进轴突分支的细胞外信号通路。此外，我们的初步研究表明，cGMP途径为分支调节提供了一种细胞内信号机制。利用原代感觉神经元培养和基因敲除小鼠，我们提出以下三个目标来进一步表征cGMP信号的作用：1)使用活体分析来建立cGMP信号作为调节不同但刻板印象的感觉神经分支发育的一般信号机制；2)确定在感觉神经分支中介导cGMP活性的下游信号机制；3)确定轴突分支的空间和时间控制的细胞机制。这些目的应该有助于在调节轴突分支的过程中建立一个独特的信号通路，并填补我们对建立突触连接的重要过程的理解的一个重大空白。此外，由于突触稳定性的丧失是许多神经疾病的标志，我们对这一基本过程的研究应该为这些疾病的病因学提供新的见解。公共卫生相关性：拟议研究的目标是调查轴突分支的分子和细胞基础，轴突分支是建立突触连接和建立神经网络的重要过程。我们将使用分子、细胞和遗传方法的组合来表征关键的分子通路，并确定调节轴突分支的信号机制。从这项研究中获得的知识不仅有助于了解大脑的发育，还将为许多神经疾病的分子基础以及如何促进中风和损伤后的神经再生提供新的见解。

DESCRIPTION (provided by applicant): Axon branching allows a neuron to communicate with multiple partners and helps establish morphologically and functionally distinct neural networks. To ensure proper synaptic connections, branching is tightly regulated by signaling pathways that allow environmental cues to instruct axons when and where to make branches. The long term goal of the proposed research is to investigate the molecular and cellular basis of this regulation, understand how it contributes to the initial development and the subsequent plastic rearrangement of synaptic connections, and provide insights into how to regenerate new branches and functional connections after injury. Using the development of stereotypic axonal branches of rodent sensory neurons from the dorsal root ganglion and trigeminal ganglion as models, we have identified an extracellular signaling pathway involving the secreted molecule Slit in promoting axon branching. In addition, our preliminary studies have demonstrated that the cGMP pathway provides an intracellular signaling mechanism for branching regulation. Using primary sensory neuron cultures and knockout mice, we propose the following three aims to further characterize the role of cGMP signaling: 1) use in vivo analysis to establish cGMP signaling as a general signaling mechanism in regulating the development of diverse yet stereotypic sensory axon branches; 2) identify the downstream signaling mechanism mediating the cGMP activity in sensory axon branching; 3) determine the cellular mechanism underlying the spatial and temporal control of axon branching. These aims should help establish a distinct signaling pathway in regulating axon branching and fill in a major gap in our understanding of an important process in making synaptic connections. In addition, since loss of synaptic stability is the hallmark of many neurological disorders, our study of this fundamental process should provide new insights into the etiology of these diseases. PUBLIC HEALTH RELEVANCE: The goal of the proposed research is to investigate the molecular and cellular basis of axon branching, an important process in making synaptic connections and establishing neural networks. We will use a combination of molecular, cellular and genetic approaches to characterize key molecular pathways and identify the signaling mechanisms underlying the regulation of axon branching. The knowledge obtained from this study will not only help understand brain development, but also provide new insights into the molecular basis of many neurological disorders as well as how to promote nerve regeneration after stroke and injury.