The Roles of Pioneer Neurons and Adhesion Molecules in Neuronal Migration

神经是我们大脑和脊髓的主要通信途径，由许多称为轴突的单独通信纤维组成。每个轴突携带来自一个神经细胞(神经元)的信息。随着胚胎的发育，这些纤维必须正确连接，才能形成正常的神经回路。在这些连接形成之前，神经元必须从它们出生的地方移动到它们将发挥作用的地方。此前，首席调查人员研究了控制面部表情的面神经的这一过程，发现一个单独的“先锋”神经元引导剩余神经元移动到它们的最终目的地。先锋神经元从哪里来，它们如何知道去哪里，其他神经元如何知道如何跟随它们？该项目将在斑马鱼胚胎(具有与人类相似的面神经的动物)的开发中解决这些问题。斑马鱼的胚胎是透明的，实验使用了特殊工程的斑马鱼，其面部神经元被荧光标记，以使它们的细胞迁移可见。实验还将检查在细胞表面发现的对细胞迁移重要的特定分子(细胞黏附分子)的作用。一种新的三维成像(光片显微镜)将被用来测量细胞运动，并将开发新的软件来可视化和分析细胞运动数据。一旦在芝加哥大学和海洋生物实验室开发和测试，这些软件工具将免费提供。该项目还将为高中生、本科生和研究生提供培训机会；向小学生和中学生介绍研究；并通过在科学与工业博物馆(MSI)的互动展示吸引公众。神经元的亚群在神经上皮平面内相切迁移，通常是在很远的距离上。为了更好地了解对神经回路形成至关重要的切向迁移机制，该项目重点研究了面部分支运动神经元(FBMN)，它经历了一种在从鱼类到哺乳动物的脊椎动物中保守的切向迁移。这项研究将利用斑马鱼胚胎，因为它们是可获得的、透明的和强大的遗传模型。迁移的FBMN将在带有基因标记细胞的透明斑马鱼胚胎中成像，并使用光片显微镜进行跟踪。首席研究员最近将先锋神经元描述为第一个在后脑两侧迁移的FBMN，并证明了这种神经元的关键作用。目标1将通过确定其细胞起源并跟踪其随后的发育轨迹来研究新发现的先锋神经元。FBMN的切向迁移也依赖于与两条不同的预先铺设的轴突束的相互作用，而这两种相互作用都依赖于黏附分子N-钙粘附素。目的2研究N-钙粘附素在FBMN和轴突束之间的相互作用中的作用，以及它在迁移过程中是否在神经元内自主发挥作用。对于FBMN迁移至关重要的其他黏附分子将使用RNAseq进行鉴定。该项目的一个组成部分将是开发新的、广泛适用的计算工具来分析成像数据。

Nerves, the major communication pathways of our brain and spinal cord, are made of many individual communication fibers called axons. Each axon carries information from one single nerve cell (neuron). As an embryo develops, these fibers have to connect up correctly in order to make working neural circuits. Before these connections can form, the neurons have to move from the place they are born to the location where they will perform their role. Previously, the Principal Investigators have studied this process in the facial nerve, which controls facial expressions, and found that a single "pioneer" neuron guides the movement of the remaining neurons to their final destinations. Where do pioneer neurons come from, how do they know where to go, and how do other neurons know how to follow them? This project will address these questions in developing zebrafish embryos (animals with facial nerves similar to humans). Zebrafish embryos are transparent, and the experiments use specially-engineered zebrafish whose facial neurons are fluorescently labeled to make their cell migration visible. Experiments will also examine the roles of particular molecules found on the cell surface that are important for cell migration (cell adhesion molecules). A new kind of 3-dimensional imaging (light sheet microscopy) will be used to measure cell movements, and new software will be developed to visualize and analyze cell movement data. Once developed and tested at the University of Chicago and the Marine Biological Laboratory, these software tools will be made freely available. The project will additionally provide training opportunities for high school, undergraduate and graduate students; introduce elementary and middle school students to research; and engage the public via interactive displays at the Museum of Science and Industry (MSI).Subsets of neurons migrate tangentially within the neuroepithelial plane, often over significant distances. To better understand mechanisms underlying tangential migration that are important for neural circuit formation, this project focuses on facial branchiomotor neurons (FBMNs), which undergo a tangential migration that is conserved in vertebrates ranging from fishes to mammals. The study will utilize zebrafish embryos as they are accessible, transparent, and a powerful genetic model. Migrating FBMNs will be imaged in transparent zebrafish embryos with genetically marked cells, and tracked using light sheet microscopy. The Principal Investigator recently described the pioneer neuron as the first FBMN to migrate on each side of the hindbrain, and demonstrated the critical role of this neuron. Aim 1 will study the newly recognized pioneer neuron by establishing its cellular origins and tracking its subsequent trajectory through development. FBMN tangential migration also relies on interactions with two different pre-laid axon tracts and both interactions depend on adhesion molecule N-Cadherin. Aim 2 will investigate the role of N-Cadherin in mediating interactions between FBMNs and axon tracts, and whether it functions autonomously within neurons during migration. Additional adhesion molecules important for FBMN migration will be identified using RNAseq. An integral part of this project will be the development of new, broadly-applicable computational tools to analyze imaging data.