Transcriptional Elements Active in Developmental and Regenerative Axon Growth

描述(申请人提供)：脊椎动物神经系统的发育和再生依赖于神经元延伸轴突的能力，轴突将与适当的突触后目标建立功能连接。虽然轴突在发育和再生期间的生长有许多相似之处，但已有研究表明，再生期间对轴突生长的某些要求与发育轴突生长有关的要求是不同的。这项研究的目的是识别基因调控元件，以响应调节再生神经系统中轴突生长的信号通路。神经生长相关蛋白(NGAP)基因的表达与轴突生长周期密切相关，因此可能成为轴突生长调控途径的靶点。一个典型的nGAP是GAP-43，一种富含在轴突生长锥体中的膜相关蛋白，在轴突生长和引导方面活跃。与其他nGAP一样，GAP-43在经历最初轴突生长和重塑的新分化神经元中表达最高，随后在轴突生长活性最低的成熟神经系统中下调。GAP-43的表达可以在成熟的神经系统中重新激活，以应对那些能够再生的神经元的损伤。介导nGAP基因转录激活和抑制的信号通路在很大程度上是未知的。本文提出的研究将使用斑马鱼的功能比较基因组学方法来剖析GAP-43基因中负责调节神经系统发育、成熟和再生过程中基因表达的特定转录调控元件。了解nGAP基因是如何调控的，对于确定如何在受损神经元中启动和维持nGAP基因的表达，以诱导正常情况下没有再生能力的神经元的再生轴突生长是重要的一步。

DESCRIPTION (provided by applicant): Development and regeneration of the vertebrate nervous system are dependent on the capacity of neurons to extend axons that will forge functional connections with the appropriate postsynaptic targets. While there are many similarities between axon growth during development and regeneration, it has been shown that some requirements for axon growth during regeneration are distinct from those involved in developmental axon growth. The goal of this research is to identify gene regulatory elements that respond to signaling pathways regulating axon growth in the regenerating nervous system. Genes encoding neuronal growth- associated proteins (nGAPs) are likely targets of axon growth regulatory pathways given the tight correlation between nGAP gene expression and periods of axon growth. A prototypical nGAP is GAP-43, a membrane- associated protein that is enriched in axonal growth cones and is active in axon growth and guidance. Like other nGAPs, GAP-43 is expressed maximally in newly differentiated neurons undergoing initial axon growth and remodeling, and is subsequently down regulated in the mature nervous system where axon growth activity is minimal. Expression of GAP-43 can be reactivated in the mature nervous system in response to injury in those neurons capable of regeneration. The signaling pathways that mediate the transcriptional activation and repression of nGAP genes are largely unknown. The studies proposed herein will use a functional comparative genomics approach in zebrafish to dissect out specific transcriptional regulatory elements within the GAP-43 gene that are responsible for regulating gene expression during nervous system development, maturation and regeneration. Understanding how nGAP genes are regulated is an important step to determining how their expression can be turned on and sustained in damaged neurons in order to induce regenerative axon growth in neurons that normally do not display a capacity for regeneration.