Molecular Mechanisms of Neuron Motility and Axon Guidance

神经元运动和轴突引导的分子机制

• 批准号: 10584813
• 负责人: John G Flanagan
• 金额: $ 166.54万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10584813
• 关键词: ASD patient; Affect; Alzheimer' s Disease; Amyloid beta-Protein; Amyloid beta-Protein Precursor; Axon; Basement membrane; Behavior; Binding; Biological; Biological Models; Biological Process; Biology; Brain; Cell Surface Receptors; Cerebral cortex; Complex; Defect; Development; Developmental Process; Dimerization; Disease; Disparate; Distal; Elements; Exons; Failure; Family; Floor; Funding; Funding Agency; Gatekeeping; Genes; Goals; Grant; In Vitro; Individual; Laminin; Lead; Life; Ligand Binding; Ligands; Link; Maps; Mediating; Membrane; Messenger RNA; Modeling; Molecular; Mus; Nervous System; Neurodegenerative Disorders; Neurodevelopmental Disorder; Neurons; Pathogenicity; Pathway interactions; Pattern; Phosphorylation; Phosphorylation Site; Physiological; Protein Biosynthesis; Protein Region; Proteins; RNA; RNA-Binding Proteins; Radial; Regulation; Research; Role; Signal Pathway; Signal Transduction; Source; Spinal; Spinal Cord; System; Technology; Testing; Therapeutic Intervention; Translations; Up-Regulation; Vertebral column; Work; autism spectrum disorder; axon guidance; cell motility; design; extracellular; gene network; genome-wide; genome-wide analysis; in vivo; insight; interest; mRNA Translation; migration; nervous system development; neurodevelopment; neuronal patterning; novel; operation; receptor; risk variant; spatiotemporal; therapeutic target

The brain relies for its function on a precise and complex pattern of neuronal connections. The broad long-term goal of this project is to understand molecular mechanisms that set up this pattern of connections during development, and how aberrations of these mechanisms lead to Alzheimer’s Disease (AD) later in life. This project focuses particularly on RNA-based regulatory mechanisms. Key advantages of regulating mRNA translation via RNA-binding proteins (RBPs) are: (1) allowing protein synthesis to be locally regulated in specific subcellular regions where the proteins are needed, and (2) coordinately regulating expression of large networks of functionally related mRNAs. To understand the basic principles of axon guidance, a major model system has been spinal commissural axon guidance at the midline. Navigating this intermediate target requires axons to be attracted and then repelled, and the classic mechanism for this is the ‘Robo switch’ where repellent Robo receptors are upregulated in post-crossing axons; however, the extracellular signal and the mechanism by which it triggers this switch have remained unknown. We have now identified a highly novel mechanism for the Robo switch, involving extracellular ligand binding to the transmembrane Amyloid Precursor Protein (APP), which interacts intracellularly with the RBP CPEB4, to regulate Robo local translation in post-crossing axon segments. Having identified this novel APP-CPEB4 pathway, the proposed studies are designed to expand our understanding of the pathway’s molecular mechanisms and functions. In commissural axon guidance, expression of many proteins is known to be locally regulated in axon segments at the midline; the proposed studies of the APP-CPEB4 pathway are expected to identify coordinate regulation of a large gene network, bringing together many disparate past observations into a unifying model for this premier paradigm of axon guidance. In addition to axon guidance, preliminary studies reveal an overlapping yet distinct set of functions for the same molecular pathway in another major developmental model system, cortical neuron migration. The novel APP-CPEB4 pathway also has high relevance to disease: in addition to its involvement in developmental processes that lead to Autism Spectrum Disorder (ASD), the pivotal role of APP in our pathway gives it key relevance to AD. Regarding autism, abnormalities at the cortical neuron migration stage are believed to be a leading cause of ASD, and CPEB4 disruption in mouse cortex at this specific stage causes ASD-like behaviors. Moreover, all the components of our pathway from ligands to downstream targets have been implicated in ASD, though not previously linked in a unifying model. Regarding AD, the transmembrane structure of APP has long led to the idea that it is a cell surface receptor, yet despite decades of intensive work no instructive receptor role – where the spatiotemporal pattern of a ligand regulates a downstream developmental or physiological function – has yet been identified for APP. Now identifying a receptor role for APP – including a pathway from ligands through a signaling pathway to functional readouts – opens the door to a qualitatively new level of understanding APP, which is especially important since the challenges of therapeutically targeting Aβ place increased emphasis on understanding the roles of APP itself. Studies of our APP-CPEB4 pathway will uncover novel biological principles, while leading to enhanced understanding of mechanisms underlying neurodevelopmental and neurodegenerative disorders. Approaches include genome-wide target mRNA identification, and functional cellular and developmental studies in vitro and in vivo. Additionally, studies of signal transduction mechanisms in the novel APP-CPEB4 pathway will be essential to understand its operation and its potential for therapeutic intervention.

大脑的功能依赖于精确而复杂的神经元连接模式。该项目的广泛长期目标是了解在发育过程中建立这种连接模式的分子机制，以及这些机制的畸变如何导致老年痴呆症（AD）。该项目特别关注基于RNA的调控机制。通过RNA结合蛋白（RBP）调节mRNA翻译的关键优势是：（1）允许在需要蛋白质的特定亚细胞区域中局部调节蛋白质合成，以及（2）协调调节功能相关mRNA的大型网络的表达。为了理解轴突引导的基本原理，主要的模型系统是中线处的脊髓连合轴突引导。导航这个中间目标需要轴突被吸引，然后被排斥，其经典机制是“Robo开关”，其中排斥性Robo受体在交叉后的轴突中上调;然而，细胞外信号及其触发这种开关的机制仍然未知。我们现在已经确定了Robo开关的一种非常新颖的机制，涉及细胞外配体与跨膜淀粉样前体蛋白（APP）结合，后者在细胞内与RBP CPEB 4相互作用，以调节交叉后轴突片段中的Robo局部翻译。在确定了这种新的APP-CPEB 4通路后，拟议的研究旨在扩大我们对该通路的分子机制和功能的理解。在连合轴突引导中，已知许多蛋白质的表达在中线的轴突节段中受到局部调节;对APP-CPEB 4通路的拟议研究预计将确定一个大型基因网络的协调调节，将许多不同的过去观察结果汇集到一个统一的模型中，用于这种首要的轴突引导范式。除了轴突引导，初步研究揭示了另一个主要发育模型系统皮质神经元迁移中相同分子通路的重叠但不同的功能集。新的APP-CPEB 4通路也与疾病高度相关：除了参与导致自闭症谱系障碍（ASD）的发育过程外，APP在我们通路中的关键作用使其与AD具有关键相关性。关于自闭症，皮质神经元迁移阶段的异常被认为是ASD的主要原因，并且在这个特定阶段小鼠皮质中的CPEB 4破坏导致ASD样行为。此外，从配体到下游靶点的途径的所有组分都与ASD有关，尽管以前没有在统一的模型中联系起来。关于AD，APP的跨膜结构长期以来导致了它是细胞表面受体的想法，然而，尽管经过几十年的深入研究，还没有发现APP的指导性受体作用--其中配体的时空模式调节下游发育或生理功能。包括从配体通过信号传导途径到功能读数的途径-打开了理解APP的质的新水平的大门，这一点尤其重要，因为治疗靶向Aβ的挑战越来越强调了解APP本身的作用。我们的APP-CPEB 4通路的研究将揭示新的生物学原理，同时导致对神经发育和神经退行性疾病的机制的理解增强。方法包括全基因组靶mRNA鉴定，以及体外和体内的功能性细胞和发育研究。此外，在新的APP-CPEB 4通路的信号转导机制的研究将是必不可少的，以了解其操作和治疗干预的潜力。