A Novel Role For Plexin A in Photoreceptor Axon Targeting

Plexin A 在光感受器轴突靶向中的新作用

• 批准号: 9195310
• 负责人: Jessica P Douthit
• 金额: $ 3.43万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9195310
• 关键词: Adhesives; Adult; Alternative Splicing; Axon; Binding; Biological Models; Brain; Cell Surface Proteins; Cells; Clone Cells; Code; Color; Color Visions; Complex; Cytoplasmic Tail; DNA Insertion Elements; Data; Defect; Development; Disease; Drosophila genus; Environment; Epilepsy; Exons; Family member; Genes; Genetic; Genetic Screening; Heart; Homologous Gene; Immune response; Intelligence; Length; Ligands; Light; Low Density Lipoprotein Receptor; Maps; Mediating; Modeling; Mutation; Nervous system structure; Neurodevelopmental Disorder; Neurons; Neuropilins; Organism; Pattern; Phenotype; Photoreceptors; Presynaptic Terminals; Process; Proteins; RNA Interference; RNA Splicing; Regulation; Retina; Role; Schizophrenia; Semaphorins; Signal Transduction; Site; Synapses; Tertiary Protein Structure; Testing; Transcript; Visual; Visual Fields; Visual system structure; Work; angiogenesis; autism spectrum disorder; axon guidance; disability; fly; genome editing; insight; knock-down; nervous system development; neural circuit; novel; null mutation; overexpression; plexin; premature; receptor; retinotopic; tumor progression; visual process; visual processing

Project Summary Formation of complex neural circuits must be precisely controlled during the development of the nervous system. Axons navigate to their targets by detecting both long-range and short-range signals presented by cells in the environment that can act as attractants or repellants. Defects in axon guidance and targeting can result in a number of neurodevelopmental disorders, such as epilepsy, schizophrenia, Autism Spectrum Disorders, and intelligence disabilities. The Drosophila visual system is an excellent model system for studying the basic mechanisms of axon guidance and neural circuit formation. The terminals of R7 and R8 photoreceptors, responsible for different aspects of color vision, are segregated into distinct target layers of the medulla, a central region of visual processing in the brain. Photoreceptors also must project in a retinotopic manner to maintain a precise representation of the visual field within the brain. In a screen for molecules that control color photoreceptor axon targeting, knocking down plexin A (plexA) in the brain using RNAi caused R7 photoreceptors to prematurely terminate in the R8 target layer of the medulla and fail to expand their axon terminals. A protein null mutation in plexA (plexAMb09499) caused by a Minos element insertion in a coding exon has the same effect on R7 axons. plexA is required in neurons, but not in photoreceptors, for R7 to reach the correct target layer. PlexA protein is expressed close to this target layer, suggesting that it may act as an attractive signal for R7 axons, in contrast to its known role in repelling L3 lamina neuron axons from this layer. Mosaic analysis will be used to confirm that this is the site of PlexA action. Overexpression of PlexA or a truncated form lacking the cytoplasmic domain in photoreceptors results in hyperfasciculation and premature termination of their axons. This misexpression phenotype will be used to characterize the mechanism of PlexA action and test the hypothesis that PlexA acts as an attractive or adhesive signal for photoreceptors. The known receptor and ligand for PlexA, Semaphorin- 1a, is not required for normal targeting of R7 photoreceptors. We will investigate whether PlexA instead interacts with an uncharacterized CUB domain protein, CG6024; knocking down CG6024 in photoreceptors using RNAi also disrupts R7 targeting. Homologs of PlexA have been studied in the organization of the vertebrate retina, and Plexin family members also participate in regulation of the immune response, heart and vessel formation, and even the progression of cancer. Preliminary results suggest that PlexA controls R7 targeting through a novel signaling mechanism, distinct from those previously described. Therefore, this work may provide new insight into the mechanisms that control a variety of developmental and disease processes in higher organisms.

项目概要 在发育过程中必须精确控制复杂神经回路的形成 神经系统。轴突通过检测远程和短程信号导航到目标 由环境中的细胞呈现，可以充当引诱剂或排斥剂。轴突缺陷 指导和靶向可能导致许多神经发育障碍，例如癫痫、 精神分裂症、自闭症谱系障碍和智力障碍。果蝇视觉系统 是研究轴突引导和神经回路基本机制的优秀模型系统 形成。 R7和R8感光器的末端，负责色觉的不同方面， 被分成不同的髓质目标层，髓质是视觉处理的中心区域 脑。感光器还必须以视网膜专题的方式投射，以保持图像的精确再现 大脑内的视野。在控制彩色感光器轴突的分子筛选中 使用 RNAi 靶向敲除大脑中的丛蛋白 A (plexA)，导致 R7 光感受器 过早地终止于髓质的 R8 目标层，并且无法扩展其轴突末端。一个 由编码外显子中的 Minos 元件插入引起的 plexA (plexAMb09499) 中的蛋白质无效突变 对 R7 轴突也有同样的作用。 plexA 在神经元中是必需的，但在光感受器中不需要，R7 才能到达 正确的目标层。 PlexA 蛋白在该靶层附近表达，表明它可能发挥作用 作为 R7 轴突的有吸引力的信号，与其已知的排斥 L3 层神经元轴突的作用相反 从这一层开始。将使用镶嵌分析来确认这是 PlexA 作用的位点。 光感受器中 PlexA 的过度表达或缺乏胞质结构域的截短形式 过度束震和轴突过早终止。这种错误表达表型将是 用于表征 PlexA 作用机制并测试 PlexA 充当 光感受器的吸引力或粘附信号。已知的 PlexA 受体和配体，Semaphorin- 1a，对于 R7 光感受器的正常靶向不需要。我们将调查是否使用 PlexA 代替 与未表征的 CUB 结构域蛋白 CG6024 相互作用；击倒 CG6024 使用 RNAi 的光感受器也会破坏 R7 靶向。 PlexA 的同系物已在 脊椎动物视网膜的组织，Plexin家族成员也参与调节 免疫反应、心脏和血管形成，甚至癌症的进展。初步结果 表明 PlexA 通过一种新颖的信号传导机制控制 R7 靶向，不同于那些 前面已经描述过。因此，这项工作可能会为控制a的机制提供新的见解。 高等生物的各种发育和疾病过程。