Neuronal primary cilium: a centralized signaling node for dendrite morphogenesis

神经元树突的大小和形状是神经元接收、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个非常短的（只有几微米长），从神经元体突出的单一信号天线，是一个集中的信号节点，对树突形态有很强的影响。这个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通性中的作用。神经元初级纤毛具有多种信号成分，作为信号中枢和环境信号传递到体细胞的中继，以实现细胞的主要功能。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谜。我的工作已经克服了这一技术限制，并建立了一个实验框架来询问发育中的神经元中的睫状体信号，我们将在这个新的NSERC项目中充分利用。在前期工作中，我们使用了Arl13b的小鼠突变体模型，Arl13b是一种纤毛特异性小GTPase，对纤毛信号转导至关重要。我们发现锥体神经元中睫状体信号的破坏显著损害了大脑皮层的树突树突化。这一建议解决了一个关键问题：初级纤毛信号如何对树突形态发生产生如此深远的影响？我们将在三个目标中：目标1。表征Arl13b突变体皮质神经元树突乔木生长和模式的改变。高分辨率共聚焦显微镜将执行树突形态的详细表征。将进行延时实时成像来分析树突乔木的生长动态。目标2。探讨纤毛驱动的细胞内信号机制在树突形态发生中的作用。我们将验证纤毛- pi3k（磷酸肌肽3-激酶）信号在调节树突发育中起核心作用的假设。我们将产生新的光遗传学工具来解剖纤毛- pi3k信号级联如何控制树突生长动力学和形态。目标3。定义纤毛信号受体调控树突形态发生。为此，我们将重点关注已知影响树突形态和在Arl13b突变体纤毛中定位错误的纤毛受体。光遗传诱导睫状体受体激活将用于直接研究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，分子遗传学和新型实验工具开发和实施方面的多样化培训。在完成这些目标后，我们将在前所未有的水平上获得关于神经元纤毛如何在发育中的大脑中起作用的变革机制的见解。

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 µm 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.