Pathfinding and target recognition by cortical axons

皮质轴突的寻路和目标识别

• 批准号: 7033875
• 负责人: DENNIS P O'LEARY
• 金额: $ 32.23万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7033875
• 关键词: DNA binding protein; axon; bone morphogenetic proteins; brain stem; chemoattractants; developmental genetics; developmental neurobiology; efferent nerve; embryo /fetus; flow cytometry; gene expression; gene targeting; genetically modified animals; growth factor receptors; immunocytochemistry; in situ hybridization; innervation; laboratory mouse; neocortex; nerve growth factors; neuroanatomy; neuronal guidance; protein localization; protein structure function; pyramidal tracts; spinal cord

We propose to study the mechanisms that control distinct phases of the development of cortical layer 5 and layer 6 efferent projections to the brainstem and spinal cord, including their pathfinding and the molecular control of their recognition and innervation of targets. We will test the hypothesis that the pioneering of the major path in and out of the cortex by cortical subplate axons through this path. This will be done by creating transgenic mice engineered to have stunted subplate axons, or lack subplate neurons altogether, and by analyzing Mash-1 mutant mice that fail to form a thalamocortical projection. To test the idea that the axonal chemoattractant, Netrin-1, molecularly defines the subcortical path of layer 5 corticospinal axons through the forebrain, midbrain and hindbrain, we will correlate this axonal path with the pattern of Netrin-1 expression, and will analyze mutant mice deficient for Netrin-1 or its receptor, DCC, for aberrant pathfinding by corticospinal axons. The remaining aims focus on target recognition by corticospinal axons, which is characterized by a de novo formation of branches along the axon shaft and their directed growth into targets. We will study the roles of BMP-3 and a novel secreted CAM-like protein with 6 Ig domains and a MAM domain (temporarily named "Ig6M"), which were isolated using a differential display PCR screen to identify candidate target recognition molecules for corticospinal axons. We will use in vitro axon guidance and branching assays, as well as gain-of-function and loss-of-function genetic experiments in mice, to determine the sufficiency and requirement of BMP-3 and Ig6M in controlling the formation and directed growth of corticospinal axon branches.

我们建议研究控制皮质第5层和第6层向脑干和脊髓的传出投射发育的不同阶段的机制，包括它们的路径以及它们识别和支配靶点的分子控制。我们将检验这一假设，即皮质亚板轴突通过这条路径是进入和离开皮质的主要路径的先驱。这将通过创造转基因小鼠来实现，这些转基因小鼠被改造成具有发育迟缓的下丘脑轴突，或者完全缺乏下丘脑神经元，并通过分析未能形成丘脑皮质投射的Mash-1突变小鼠来实现。为了测试轴突趋化剂Netrin-1在分子上定义了第5层皮质脊髓轴突通过前脑、中脑和后脑的皮质下路径的想法，我们将把这条轴突路径与Netrin-1的表达模式相关联，并将分析Netrin-1或其受体DCC缺失的突变小鼠，以寻找皮质脊髓轴突的异常路径。剩下的目标集中在皮质脊髓轴突的靶标识别上，其特征是沿着轴突轴突形成新的分支，并定向生长为靶标。我们将研究BMP-3和一种新的分泌型CAM样蛋白的作用，该蛋白具有6个Ig结构域和一个MAM结构域(临时命名为“Ig6M”)，这两个蛋白是通过差异显示PCR筛选出皮质脊髓轴突的候选靶标识别分子。我们将使用体外轴突引导和分支分析，以及小鼠功能获得和功能丧失的遗传学实验，以确定BMP-3和Ig6M在控制皮质脊髓轴突分支的形成和定向生长方面的充分性和必要性。