Approaches to studying axon fasciculation

描述（由申请人提供）：了解轴突如何找到它们的突触目标是神经发育的一个基本问题。虽然在阐明轴突引导的机制方面已经取得了很大的进展，但对于轴突如何在神经束的特定区域内束状结构知之甚少。我们建议在秀丽隐杆线虫中以HSN轴突为重点研究这一问题。整个神经系统建立后，HSN轴突沿腹侧神经索延伸。HSN生长锥沿PVQ和PVP轴突呈束状分布，该项目的短期目标是确定HSN沿其在神经束中的特定路径生长的能力的线索。虽然人们对哺乳动物神经中轴突的束状结构知之甚少，但最近的研究结果表明，神经中嗅觉轴突的分类对于它们靶向嗅球很重要。HSN可能为哺乳动物的神经结构提供了一个模型。该提案有三个具体目标。在第一个目标中，不同轴突之间的界面将使用GRASP进行标记。在第二个目标，RNAi方法鉴定基因参与HSN轴突的束控将被开发。这些方法应该绕过由必需基因的RNAi引起的致命影响和由其他轴突的早期束控缺陷引起的间接影响。在第三个目标中，将对这些方法进行测试，以阐明神经递质乙酰胆碱在轴突束化中的作用。

DESCRIPTION (provided by applicant): Understanding how axons find their synaptic targets is a fundamental problem in neurodevelopment. While great progress has been made in elucidating the mechanisms of axon guidance, less is known about how axons fasciculate within specific regions of a nerve bundle. We propose to study this problem in C. elegans with a focus on the HSN axon. The HSN axon extends along the ventral nerve cord after the entire nervous system has been established. The HSN growth cone fasciculates along the PVQ and PVP axons, and the short-term goal of this project is to identify the cues that define the HSN's ability to grow along its specific path in the nerve bundle. While little is known about how axons fasciculate within mammalian nerves, recent findings suggest that sorting of olfactory axons within the nerve are important in their targeting at the olfactory bulb. The HSN may provide a model for how such nerves are organized in mammals. The proposal has three specific aims. In the first aim, the interface between the different axons will be labeled using GRASP. In the second aim, RNAi approaches to identify genes involved in HSN axon fasciculation will be developed. These approaches should bypass the lethal effects caused by RNAi of essential genes and indirect effects caused by earlier defects in the fasciculation of other axons. In the third aim, the approaches will be tested to elucidate the role of the neurotransmitter acetylcholine in axon fasciculation.. PUBLIC HEALTH RELEVANCE: Understanding how these axons find their targets is a fundamental problem in neurodevelopment. While great progress has been made in elucidating the mechanisms of axon guidance, less is known about how axons grow along specific regions of a nerve bundle. We propose to study this problem in C. elegans, a model organism that has been instrumental in defined conserved molecules that function axon guidance.