Regulation of axon outgrowth by retrograde Ret signaling

在发育过程中或损伤后，轴突终末必须在复杂的环境中导航才能形成 功能连接。Ret是一种神经营养因子受体，存在于生长轴突的尖端。Ret 活化和内化诱导活化受体向细胞体的逆行转运， 转录反应，这反过来又促进轴突生长。尽管它在神经系统中起着重要作用， 系统的发展，目前还不知道如何激活Ret受体是在轴突中贩运，的性质， 逆行Ret信号诱导的转录反应，以及这些转录靶点如何 最终促进轴突生长。为了解决这些问题，我们正在利用斑马鱼的独特优势， 包括活体成像和遗传学方法，以确定控制逆行的分子机制， 神经营养因子受体Ret的转运和随后的转录反应。在我们的初步调查中 研究中，我们发现Ret的逆行转运依赖于与支架蛋白Jip 3的结合， 将货物连接到逆行马达上进行运输。ret和jip 3突变体都显示出截短的感觉轴突， 实时成像显示异常的生长锥动力学和减少的轴突末端加工。使用RNA 通过测序，我们鉴定了许多响应Ret-Jip 3的转录诱导因子 逆行信号传导，并且在这种情况下是基于肌动蛋白的逆行行为的假定调节剂。基于 根据这些数据，我们假设Ret的Jip 3依赖性逆行转运诱导了促进生长的因子， 感觉轴突延伸所需的视锥动力学。我们将在三个具体目标中检验这一假设。在 目的1、明确Ret逆行转运的分子机制及Jip 3在其中的作用。 第二个目标的实验将确定导致轴突失败的生长锥动力学缺陷 在ret和jip 3突变体的延伸，并确定在这一过程中的Ret逆行信号的作用。的 最后一个目的是研究逆行Ret信号引起的转录反应，以及如何影响Ret信号的转录。 受此转录程序调控的基因促进生长锥动力学。总之，我们的研究 将斑马鱼的创新试验与体内技术相结合，以确定逆行的特定作用。 神经营养因子信号传导在轴突生长中的作用。我们的工作将进一步揭示长距离免疫的机制。 神经营养因子信号被转导到调节生长锥动力学和轴突的细胞反应中， 扩展名.

During development or following injury, axon terminals must navigate through a complex environment to form functional connections. Ret is a neurotrophin receptor which is present at the tips of growing axons. Ret activation and internalization induces retrograde transport of the activated receptor to the cell body triggering a transcriptional response, which in turn promotes axon outgrowth. Despite its essential role during nervous system development, it is not known how activated Ret receptor is trafficked in axons, the nature of the transcriptional response induced by the retrograde Ret signaling, and how these transcriptional targets ultimately promote axon growth. To address these questions, we are using the unique advantages of zebrafish, including live imaging and genetic approaches, to identify the molecular mechanisms that govern retrograde transport of a neurotrophin receptor Ret and the subsequent transcriptional response. In our preliminary studies, we discovered that retrograde transport of Ret depends on binding to the scaffold protein, Jip3, which links cargo to the retrograde motor for transport. Both ret and jip3 mutants display truncated sensory axons, and live imaging revealed abnormal growth cone dynamics and reduced axon terminal elaboration. Using RNA sequencing, we identified a number of factors that are transcriptionally induced in response to Ret-Jip3 retrograde signaling and are putative regulators of actin-based protrusive behavior in this context. Based on this data, we hypothesize that Jip3-dependent retrograde transport of Ret induces factors that promote growth cone dynamics required for sensory axon extension. We will test this hypothesis in the three specific aims. In Aim 1, we will define the molecular mechanisms of Ret retrograde transport and the role of Jip3 in this process. Experiments in the second aim will define the defects in growth cone dynamics that lead to the failure of axon extension in ret and jip3 mutants and determine the role of the Ret retrograde signaling in this process. The last aim will investigate the transcriptional response elicited by the retrograde Ret signaling and how factors that are regulated by this transcriptional program promote growth cone dynamics. Altogether, our study combines innovative assays in zebrafish with in vivo techniques to determine the specific role of retrograde neurotrophin signaling in axon outgrowth. Our work will further uncover the mechanisms by which long-range neurotrophin signals are transduced into cellular responses that regulate growth cone dynamics and axon extension.