Transcriptional Elements Active in Developmental and Regenerative Axon Growth

描述（由申请人提供）：脊椎动物神经系统的发育和再生依赖于神经元扩展轴突的能力，轴突将与适当的突触后靶点形成功能连接。虽然轴突在发育和再生过程中的生长有许多相似之处，但研究表明，再生过程中轴突生长的一些要求与发育轴突生长的要求不同。本研究的目的是确定在再生神经系统中对调节轴突生长的信号通路作出反应的基因调控元件。考虑到神经元生长相关蛋白（nGAPs）基因的表达与轴突生长周期密切相关，编码nGAPs的基因可能是轴突生长调控途径的靶点。典型的nGAP是GAP-43，这是一种富含轴突生长锥的膜相关蛋白，在轴突生长和引导中起作用。与其他ngap一样，GAP-43在初分化的神经细胞轴突生长和重塑中表达最多，随后在轴突生长活性最低的成熟神经系统中表达下调。在成熟神经系统中，具有再生能力的神经元损伤后，GAP-43的表达可被重新激活。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。本文提出的研究将在斑马鱼中使用功能比较基因组学方法来解剖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基因是如何被调控的是确定其如何在受损神经元中表达并维持以诱导通常不显示再生能力的神经元的再生轴突生长的重要一步。

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.