Dynamic interactions among olfactory sensory neuron axons

项目摘要-摘要 当配体与分子受体结合时，嗅觉开始于嗅觉上皮(OE) 表达于嗅觉感觉神经元的纤毛。巴克和阿克塞尔(1991)是第一个 描述编码气味受体(ORs)的基因大家族，目前已知的基因数量约为1,200 老鼠。OSN仅表示1或。表达相同OR的OSN不会聚集，而是广泛存在 分布在整个OE中。因此，OE是一个复杂的神经元马赛克，每个神经元只表达一个 1200次可能的手术。当OSN轴突离开OE时，它们最初与最近的邻居捆绑在一起，而不是 必然与OSN的轴突表达相同的OR。然而，当它们在地表上前进时 从嗅球到肾小球汇合点，轴突经历一种深刻的地形学变化。 重组，使所有来自表达相同OR的神经元的轴突汇聚为 2/3肾小球/嗅球。轴突的重组和汇聚成特定的肾小球的过程 在脊椎动物中广泛保守，并构成一个重大的布线问题，可能是最复杂的 在感官系统中发现布线问题。尽管各方一致努力确定分子底物 关于OSN轴突的生长、融合和靶向，我们仍然可悲地对最基本的 轴突的方面：轴突相互作用：OSN轴突的重组如何与组织 他们的轴骨和细胞器？轴突最初形成束状和轴突时，轴骨骼动力学是什么 向OB延伸，当它们在嗅神经层脱叉时，形成新的或同型的 针对特定肾小球的束状物？是什么推动了OSN轴突的分束/散布；是什么 牵涉到机械力吗？我们什么时候才能认识到同型颤动？会议的时间表是什么？ OSN的成熟及其与轴突向OB靶点和功能的延伸有何关系 活动?重要的是，这些基本问题同样适用于所有脊椎动物，其中嗅觉系统 发展遵循同样的基本规律。因此，在这里，除了研究轴突：轴突相互作用和 在小鼠的超微结构方面，我们引入了一种新的模型，斑马鱼的活体成像，以评估其动态性质 OSN轴突：发育过程中轴突的相互作用。开始解决我们的 知识我们提出3个具体目标：目标1-关于细胞骨架组织的测试假设 大鼠嗅神经层内、外亚层OSN轴突及其束状分布 嗅球。目标2-测试以下假设：轴骨骼动力学以及机械力， 控制活斑马鱼OSN轴突的分束/散布和导航。目标3-测试 OSN轴突延伸的时空动力学与细胞骨架表达的假说 而黏附分子在围产期和成年小鼠中有所不同。

Project Summary – Abstract Odor perception begins in the olfactory epithelium (OE) when ligands bind to molecular receptors expressed on the cilia of the olfactory sensory neurons (OSNs). Buck and Axel (1991) were the first to describe the large family of genes coding for the odorant receptors (ORs), now known to number ~1,200 in mice. An OSN expresses only 1 OR. OSNs expressing the same OR do not cluster but rather are broadly distributed across the OE. Thus, the OE is a complex mosaic of neurons each of which expresses only 1 of 1,200 possible ORs. As OSN axons exit the OE they initially fasciculate with nearest neighbors, not necessarily with axons from OSNs expressing the same OR. However, as they progress over the surface of the olfactory bulb to a point of glomerular convergence, the axons undergo a profound topographical reorganization such that all of the axons coming from neurons expressing the same OR converge into only 2/3 glomeruli/olfactory bulb. This process of reorganization of axons and convergence into specific glomeruli is broadly conserved among vertebrates and poses a significant wiring problem, perhaps the most complex wiring problem found among sensory systems. Despite concerted efforts to identify the molecular substrates of OSN axon growth, coalescence and targeting, we remain woefully ignorant of the most fundamental aspects of axon:axon interactions: How does the reorganization of OSN axons relate to the organization of their axoskeleton and organelles? What are the axoskeleton dynamics as axons initially fasciculate and extend toward the OB and when they defasciculate in the olfactory nerve layer, forming new OR homotypic fascicles targeted to specific glomerului? What drives fasciculation/defasciculation of OSN axons; are mechanical forces involved? When do we recognize homotypic fasciculation? What is the timeline for the maturation of OSNs and how does it relate to the extension of the axon to OB targets and functional activity? Importantly, these fundamental questions apply equally to all vertebrates, in which olfactory system development obeys the same basic rules. Thus here, in addition to studies of axon:axon interactions and ultrastructure in mice, we introduce a new model, live imaging in zebrafish, to assess the dynamic nature of OSN axon:axon interactions during development. To begin addressing these significant gaps in our knowledge we propose 3 specific aims: Aim 1 - Test hypotheses regarding the cytoskeletal organization of OSN axons and their fasciculation in the inner and outer sublaminae of the olfactory nerve layer of the olfactory bulb. Aim 2 – Test the hypotheses that the axoskeleton dynamics, as well as mechanical forces, control the fasciculation/defasciculation and navigation of OSN axons in the live zebrafish. Aim 3 – Test the hypothesis that the spatio-temporal dynamics of OSN axon extension and the expression of cytoskeletal and adhesion molecules differ in perinatal versus adult mice.