Regulation of axonal arbor and synaptic dynamics by the apoptotic pathway: Interactions with the cytoskeleton, downstream substrates and upstream regulators

神经元之间适当连接的形成和维持对神经系统的正常功能至关重要。这些过程中的缺陷可能导致行为障碍和改变。在中枢神经系统（CNS）中，突触的形成依赖于突触前和突触后轴突和树突分支的调节加工和相互作用。因此，树枝状结构和突触发生在确保突触连接的正确模式和同时定义神经元的复杂和区室化几何结构方面至关重要。这种区室化使得细胞信号传导途径能够划分，这是至关重要的，特别是如果涉及的信号级联具有多效性效应或甚至可能损害整个细胞。我最近表明，半胱天冬酶，细胞凋亡的关键介质，激活本地年轻，动态轴突乔木的分支点，并在乔木生长过程中维持轴突和突触动力学的关键。 为此，我利用了斑马鱼幼虫，由于其体积小，透明度和遗传可塑性，提供了一个前所未有的机会，在体内研究脊椎动物中枢神经系统的神经细胞生物学。连接视网膜和中脑顶盖的视网膜顶盖投射是突触特异性的重要发育模型。在这个应用程序中，我建议解决一个重要的差距，在我们的知识的作用，当地的信号转导途径乔木动态：我们不明白半胱天冬酶介导的分支动态，这必须涉及调制的细胞骨架，什么细胞生物学翻译成形态发生事件或如何调节上游信号，以避免细胞死亡的细胞骨架变化。也不知道是否神经活动的独立和活动依赖机制调节乔木生长共享类似的机制。通过在体内活成像的树枝化和突触的形成，基因功能和视觉刺激模式的操纵相结合，我建议研究的细胞和分子生物学的半胱天冬酶在发展和经验依赖的乔木和突触动力学。具体来说，我计划：1。明确树状化和突触发生的细胞骨架动力学，并确定caspase激活如何以及在何处促进树状化和突触前重塑的细胞骨架变化。2.）的情况。确定下游半胱天冬酶靶点以及它们如何修饰细胞骨架。3.）第三章探讨caspase活性在乔木中是如何通过外在或内在凋亡途径和视觉体验进行动态和局部调节的。 我的研究将提供关键的机制洞察神经元树枝化和突触形成，我的研究将确定一组细胞和分子的组成部分和原则，在神经元，这可能会转移到非凋亡过程中的其他细胞环境。

The formation and maintenance of appropriate connections between neurones are critical to the normal functioning of the nervous system. Defects in these processes can lead to disorders and alterations in behaviour. In the central nervous system (CNS), synapse formation depends on the regulated elaboration and interaction of pre- and post-synaptic axonal and dendritic branches. Arborisation and synaptogenesis are hence critical in ensuring the proper pattern of synaptic connections and at the same time in defining the complex and compartmentalised geometry of neurones. This compartmentalisation enables the partitioning of cellular signaling pathways, which is critical especially if signaling cascades involved have pleiotropic effects or that could even harm the cell as a whole. I have recently shown that caspases, key mediators of apoptosis, are activated locally at branch points of young, dynamic axonal arbors and are key in maintaining axonal and synaptic dynamics during arbor growth. For this, I took advantage of zebrafish larvae, which owing to their small size, transparency and genetic malleability, offer an unprecedented opportunity to study neuronal cell biology in vivo in the vertebrate CNS. The specific focus on the retinotectal projection, which connects the retina to the midbrain tectum, has long served as an important developmental model of synaptic specificity. In this application, I propose to address an important gap in our knowledge about the role of local signaling pathways in arbor dynamics: We do not understand how caspases mediate branch dynamics, which must involve modulation of the cytoskeleton, what cell biology translates such cytoskeletal changes into morphogenic events or how it is regulated by upstream signals to avoid cell death. It is also not known whether neural activity-independent and activity-dependent mechanisms regulating arbor growth share similar mechanisms. Via a combination of in vivo live imaging of arborisation and synapse formation, manipulation of gene function and visual stimulation patterns, I propose to study the cell and molecular biology of caspases during developmental and experience-dependent arbor and synaptic dynamics. Specifically I plan: 1.) To define the underlying cytoskeletal dynamics of arborisation and synaptogenesis and to identify how and where caspase activation promotes the cytoskeletal changes underlying arbor and presynaptic remodeling. 2.) To identify downstream caspase targets and how they modify the cytoskeleton. 3.) To determine how caspase activity is dynamically and locally regulated in arbors via the extrinsic or intrinsic apoptosis pathways and visual experience. My studies will provide key mechanistic insights into neuronal arborisation and synapse formation and my research will identify a set of cellular and molecular components and principles in neurones, which may be transferred to nonapoptotic processes in other cellular contexts.