Assessing the contact-mediated role of netrin1 in axon guidance

评估 netrin1 在轴突引导中的接触介导作用

• 批准号: 9815911
• 负责人: SAMANTHA J BUTLER
• 金额: $ 44.44万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9815911
• 关键词: Adhesions; Adhesives; Axon; Biological Assay; Cells; Chemotaxis; Chickens; Collection; Complex; Cues; Data; Deposition; Development; Diffuse; Disease; Embryo; Environment; Event; Family; Floor; Ganglia; Genetic; Geometry; Goals; Growth; Growth Cones; Hedera; Image; In Vitro; Injury; Laminin; Lateral; Maps; Mediating; Membrane; Modeling; Molecular; Mus; Muscle fasciculation; Mutation; Natural regeneration; Nervous system structure; Neurodevelopmental Disorder; Neurons; Phenotype; Plant Roots; Play; Positioning Attribute; Process; Prosencephalon; Radial; Resolution; Role; Signal Transduction; Source; Spinal; Spinal Cord; Surface; Synapses; Telencephalon; Textbooks; Tissues; Ventricular; axon growth; axon guidance; axonal guidance; brain malformation; cell growth; cell type; corticofugal fiber; diencephalon; domain mapping; genetic approach; member; nerve stem cell; neural circuit; receptor; regenerative; repaired; uptake

The establishment of neural circuits requires neurons to extend axons over considerable distances, using molecular cues in the embryonic environment to orient their growth cones. The textbook example of a guidance factor is netrin1, a member of the laminin superfamily first characterized in the spinal cord. Classic studies suggested that netrin1, produced by floor plate (FP) cells, acts by chemotaxis, diffusing over long distances to guide Dcc+ commissural axons towards the FP. Netrin1 was then implicated in guidance decisions throughout the nervous system. However, our studies have recently demonstrated that the key source of netrin1 is neural progenitor cells (NPCs) in the spinal ventricular zone. Rather than acting as a long-range diffusible gradient, our data supports a model in which NPC-derived netrin1 acts locally, forming a directional path for axons that also promotes axonal fasciculation. The bipolar geometry of NPCs permits them to deposit netrin1 at the basal (pial) margins of the spinal cord. This netrin1+ substrate then acts locally to direct fasciculated, ventral axon extension by haptotaxis, the directed growth of cells along an adhesive surface. However, netrin1 may mediate a more complex activity for axons beyond pure adhesion: netrin1 is then deposited onto Dcc+ axons, and these axons then grow precisely around the border of VZ, i.e. a netrin1- expressing domain. Ablating a small region of netrin1 expression causes axons deviate from their trajectory to follow the ectopic netrin1 boundary. We propose to call this collection of activities a “hederal” growth boundary, from the analogy of a wall supporting the growth of ivy (genus: hedera) that is not itself penetrated by the ivy. Netrin1 can form a local growth substrate, and promote the fasciculated growth of axons around a netrin1-expressing domain. This reinterpretation of the mechanistic basis by which netrin1 functions, explains why little progress has been made using soluble netrin1 as a regenerative factor. To further this goal, we will assess [1] the mechanisms by which spinal NPCs establish a netrin1+ haptotactic substrate that promotes directed, fasciculated axonal growth in Aim 1, [2] whether NPC vs FP cells have distinct roles producing netrins in Aim 2 and [3] whether netrins have haptotactic activities in axon guidance in the forebrain in Aim 3. Aim 1: Determine the mechanism by which spinal NPCs establish netrin1 “hederal” boundaries Hypothesis: Spinal NPCs traffic netrin1 to the pial surface to establish a haptotactic substrate. Netrin1 then transfers to Dcc+ axons to promote their fasciculated axon growth around netrin1-expressing regions. Aim 2: Determine the range role of FP-derived netrin1 in the spinal cord Hypothesis: FP-derived netrin1 acts over short range to fasciculate commissural axons crossing the midline Aim 3: Determine the role of NPC-derived netrin1/3 in the forebrain Hypothesis: Neural progenitors in the developing forebrain use the netrin family to establish growth boundaries that guide axons between the diencephalon and telencephalon.

神经元的建立要求神经元延伸轴突超过考虑 距离，使用胚胎环境中的分子提示定向其生长锥。教科书 引导因素的示例是Netrin1，这是脊柱中首次表征的层粘连蛋白超家族的成员 绳索。经典研究表明，由地板板（FP）细胞产生的Netrin1通过趋化性作用，扩散 在长距离的情况下，将DCC+连合轴突引导到FP。然后Netrin1与 整个神经系统的指导决策。但是，我们的研究最近表明 Netrin1的关键来源是脊柱心室区域中的神经祖细胞（NPC）。而不是充当 远程扩散梯度，我们的数据支持一个模型，其中NPC衍生的Netrin1在本地起作用，形成了一个模型 轴突的定向路径也促进了轴突束缚。 NPC的双极几何形状允许它们 将netrin1沉积在脊髓的子宫内（PIAL）边缘。然后，此Netrin1+底物在本地作用于 直接引起的，腹侧轴突通过触觉延伸，沿粘合剂的细胞的定向生长 表面。但是，netrin1可能会介导纯粘合剂以外的轴突更复杂的活动：netrin1是 然后沉积在DCC+轴突上，然后这些轴突精确地生长在VZ的边界周围，即Netrin1- 表达域。减轻Netrin1表达的一小部分会导致轴突偏离其轨迹到 遵循Ecopic Netrin1边界。我们建议将此活动称为“猎人”的增长 边界，从支持常春藤生长的墙的类比（属：hedera）本身都没有穿透 由常春藤。 Netrin1可以形成局部生长基材，并促进轴突周围的轴突的突出生长 Netrin1表达域。 Netrin1功能的机理基础的这种重新解释，解释了 为什么使用固体Netrin1作为再生因素几乎没有取得进展。为了进一步这个目标，我们将 评估[1]脊柱NPC建立Netrin1+ haptotactic底物的机制 AIM 1中的定向，着迷的轴突生长[2] NPC与FP细胞是否具有不同的作用，产生了Netrins 在AIM 2和[3]中，Netrins在AIM 3中的前脑中是否具有抗脉络性活性。 AIM 1：确定脊柱NPC建立NetRin1“ Hederal”边界的机制 假设：脊柱NPCS交通Netrin1到pial表面以建立触觉底物。然后Netrin1 转移到DCC+轴突，以促进其表达Netrin1周围的轴突生长。 AIM 2：确定FP衍生的Netrin1在脊髓中的作用 假设：FP衍生的Netrin1在短范围内起作用，突破了中线的连锁轴突 AIM 3：确定NPC衍生的Netrin1/3在前脑中的作用 假设：发展前脑中的神经祖细胞使用Netrin家族建立生长界限 该指导脑膜和脑脑之间的轴突。