Neuronal primary cilium: a centralized signaling node for dendrite morphogenesis

神经元初级纤毛：树突形态发生的集中信号节点

• 批准号: RGPIN-2019-04820
• 负责人: Guo, Jiami
• 金额: $ 2.99万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=688318
• 关键词: Neuronal; primary; cilium; centralized; signaling

The appropriate size and shape of neuronal dendritic arbors is a key determinant of how neurons receive, integrate, and encode circuit information. We recently made an unexpected finding that the neuronal primary cilium, a remarkably short (just a few m long), singular signaling antenna that protrudes from the neuronal soma, is a centralized signaling node that robustly influences dendrite morphology. The goal of this NSERC DG Research Program is to define the role of the neuronal primary cilium in neuronal morphogenesis and connectivity. ******The neuronal primary cilium possesses a diverse cast of signaling components to act as a signaling hub and relay of environmental signals to the soma for major cell functions. However, due to a lack of methods to precisely control cilia-specific signaling events, the exact role of ciliary signaling in overall brain development and function remains enigmatic. My work has overcome this technical limitation and established an experimental framework to interrogate ciliary signaling in developing neurons, which we will fully exploit in this new NSERC project. ******In preliminary work, we used a mouse model mutant for Arl13b, a ciliary-specific small GTPase critical for ciliary signal transduction. We found that disruption of ciliary signaling in pyramidal neurons significantly impairs dendritic arborization in the cerebral cortex. This proposal addresses a key question: How does primary ciliary signaling exert such profound effects on dendrite morphogenesis? In three aims, we will: ******Aim 1. To characterize the altered dendritic arbor growth and patterning in Arl13b mutant cortical neurons. High-resolution confocal microscopy will be performed for a detailed characterization of the dendritic morphology. Time-lapse live imaging will be performed to analyze the dendritic arbor growth dynamics.******Aim 2. To delineate the ciliary-driven intracellular signaling mechanisms in dendrite morphogenesis. We will test the hypothesis that the ciliary-PI3K (Phosphoinositide 3-kinase) signaling plays a central role in modulating dendrite development. We will generate novel optogenetic tools to dissect how ciliary-PI3K signaling cascades govern dendritic growth dynamics and morphology. ******Aim 3. To define the ciliary signaling receptors that modulate dendrite morphogenesis. We will focus on the ciliary receptors known to influence dendrite morphology and mislocalized in Arl13b mutant cilia for this aim. Optogenetically induced ciliary receptor activation will be used to directly examine these receptors' influence on dendrite morphology development. ******Each aim is specifically designed to provide HQP with diverse training in neurodevelopment, molecular genetics, and novel experimental tool development and implementation. Upon completion of these aims, we will have gained transformative mechanistic insights into how neuronal cilia function in the developing brain at a level never before achieved. *****

神经元树突轴的适当大小和形状是神经元如何接收、整合和编码电路信息的关键决定因素。我们最近有了一个意想不到的发现，神经元初级纤毛是一种非常短（只有几米长）的、从神经元胞体伸出的单一信号天线，是一个强烈影响树突形态的集中信号节点。 NSERC DG 研究计划的目标是确定神经元初级纤毛在神经元形态发生和连接中的作用。 ******神经元初级纤毛拥有多种信号成分，可作为信号中枢并将环境信号传递至体细胞以实现主要细胞功能。然而，由于缺乏精确控制纤毛特异性信号事件的方法，纤毛信号在整个大脑发育和功能中的确切作用仍然是个谜。我的工作克服了这一技术限制，并建立了一个实验框架来研究神经元发育过程中的纤毛信号传导，我们将在这个新的 NSERC 项目中充分利用该框架。 ******在初步工作中，我们使用了 Arl13b 的小鼠模型突变体，Arl13b 是一种对纤毛信号转导至关重要的纤毛特异性小 GTP 酶。我们发现锥体神经元纤毛信号传导的破坏会显着损害大脑皮层的树突状树枝化。该提案解决了一个关键问题：初级纤毛信号传导如何对树突形态发生产生如此深远的影响？我们将实现三个目标： ******目标 1. 表征 Arl13b 突变皮层神经元中树突乔木生长和模式的改变。将进行高分辨率共焦显微镜以详细表征树突形态。将进行延时实时成像来分析树突乔木的生长动态。******目标 2. 描述树突形态发生中纤毛驱动的细胞内信号传导机制。我们将检验纤毛-PI3K（磷酸肌醇 3-激酶）信号在调节树突发育中发挥核心作用的假设。我们将开发新型光遗传学工具来剖析纤毛-PI3K 信号级联如何控制树突生长动力学和形态。 ******目标 3. 定义调节树突形态发生的纤毛信号受体。为此，我们将重点关注已知影响树突形态并在 Arl13b 突变体纤毛中错误定位的纤毛受体。光遗传学诱导的纤毛受体激活将用于直接检查这些受体对树突形态发育的影响。 ******每个目标都是专门为 HQP 提供神经发育、分子遗传学以及新型实验工具开发和实施方面的多样化培训而设计的。完成这些目标后，我们将获得关于神经元纤毛如何在发育中的大脑中以前所未有的水平发挥作用的变革性机制见解。 *****