Mechanisms governing Nuclear Factor I gene induction and function during the ini

描述(申请人提供)：神经胶质细胞约占成人中枢神经系统(CNS)细胞组成的90%，支持多种对中枢神经系统功能至关重要的生理作用。然而，控制体内多潜能神经干细胞启动胶质形成的分子过程仍然知之甚少。因此，这一提议的首要目标是阐明支配神经干细胞启动神经胶质形成的机制。我们最近证实，核因子I(NFI)基因控制着胚胎脊髓中神经胶质细胞的生成，并且在神经干细胞群体中被诱导，这与体内神经胶质细胞发生的开始是一致的。这些特性使NFI基因成为研究诱导和维持胶质形成早期阶段的基因调控程序的理想起点。因此，我们假设，对与NFI基因调控相关的上游和下游事件的剖析将为胶质形成的分子控制提供新的见解。这项建议的具体目标1和2是基于我们在胚胎脊髓中发现的两个不同的NFI基因表达调节因子。通过对NFIA启动子的增强子筛选，我们已经确定了一个高度保守的增强子元件(E123)，当将其导入鸡胚胎脊髓时，它概括了NFIA诱导的空间和时间模式。因此，在目标1中，我们建议利用e123作为一种工具来识别控制NFIA诱导的核心转录因子集。我们还发现，骨形态发生蛋白(BMP)信号以一种独立于目标1中研究的e123增强子的方式控制胚胎脊髓中NFI基因的表达。因此，在目标2中，我们计划确定NFIA启动子中的BMP反应元件，确定BMP信号在NFI基因表达调控中的特定作用，并确定BMP信号确实独立于调控e123诱导的转录控制机制。最后，目标3是神经干细胞基因表达时间谱研究的合理扩展，在该研究中，我们确定了一组在NFI基因诱导后在胚胎脊髓中上调的基因。初步研究表明，在没有NFIA的情况下，这些基因中的四个足以恢复胶质形成，这表明它们的功能位于NFI基因的下游。我们将在体内使用功能获得和功能丧失的方法来发现这些基因是否以及如何促进胶质形成以及在胶质形成启动期间如何促进NFI基因下游的功能。在这些研究完成后，我们希望有一个更全面的分子过程图，包括NFI基因的上游和下游，这些基因控制着中枢神经系统发育过程中胶质形成的启动。由此产生的对指定对神经胶质细胞谱系的承诺的信号的洞察应该会将对胚胎脊髓中神经胶质细胞规格的理解从推测领域提升到可以开始考虑临床应用的程度。 与公共健康相关：该项目关注控制神经胶质细胞生成的分子过程。神经胶质细胞与多种癌症和神经系统退行性疾病有关，了解控制它们产生的发育过程是开发这些疾病新的治疗方法的关键。这一建议围绕着一个基因家族，该基因家族控制着神经胶质细胞的生成，在星形细胞瘤中也有表达，并有助于它们的形成。因此，本文的研究直接适用于对星形细胞瘤的认识和治疗。

DESCRIPTION (provided by applicant): Glial cells comprise approximately 90% of the cellular constituency of the adult central nervous system (CNS) and support a vast array of physiological roles essential to CNS function. Yet, the molecular processes that control the initiation of gliogenesis from multipotent neural stem cells in vivo remain poorly understood. Thus, the overriding goal of this proposal is to elucidate the mechanisms that govern the initiation of gliogenesis from neural stem cells. We recently demonstrated that nuclear factor I (NFI) genes control the generation of glial cells in the embryonic spinal cord and are induced in neural stem cell populations coincident with the onset of gliogenesis in vivo. These properties make the NFI genes an ideal starting point from which to investigate the genetic regulatory programs that induce and maintain the early stages of gliogenesis. We, therefore, hypothesize that dissection of both the upstream and downstream events associated with NFI gene regulation will provide novel insights into the molecular control of gliogenesis. Specific Aims 1 and 2 of this proposal are based on our discovery of two distinct regulators of NFI gene expression in the embryonic spinal cord. Using enhancer screening of the NFIA promoter we have identified a highly conserved enhancer element (e123) that recapitulates the spatial and temporal patterns of NFIA induction when introduced into the embryonic chick spinal cord. Thus, in Aim 1 we propose to exploit e123 as a tool to identify a core set of transcription factors that control NFIA induction. We have also found that bone morphogenic protein (BMP) signaling controls NFI gene expression in the embryonic spinal cord in a manner that is independent of the e123 enhancer studied in Aim 1. Therefore, in Aim 2 we plan to identify BMP-responsive elements in the NFIA promoter, define the specific role of BMP signaling in the regulation of NFI gene expression, and to establish that BMP signaling does indeed operate independently of the transcriptional control mechanisms that regulate e123 induction. Finally, Aim 3 is a logical extension of temporal profiling studies of gene expression in neural stem cells in which we identified a cohort of genes upregulated after NFI gene induction in the embryonic spinal cord. Preliminary studies indicate that four of these genes are sufficient to restore gliogenesis in the absence of NFIA, suggesting that they function downstream of NFI genes. We will use gain- and loss-of function approaches in vivo to discover whether and how these genes promote gliogenesis and function downstream of NFI genes during the initiation of gliogenesis. Upon completion of these studies, we expect to have a much more comprehensive map of molecular processes, both upstream and downstream of NFI genes that control the initiation of gliogenesis during CNS development. The resultant insights into the signals that specify commitment to the glial lineage should lift understanding of glial cell specification in the embryonic spinal cord from the speculative realm to a point where clinical applications can begin to be considered. PUBLIC HEALTH RELEVANCE: This project focuses on the molecular processes that control the generation of glial cells. Glial cells have been implicated in a vast array of cancers and degenerative diseases of the nervous system and understanding the developmental processes that control their generation is a key to developing new therapeutic approaches to these disorders. This proposal is centered around a gene family that controls the generation of glial cells and is also expressed in astrocytomas and contributes to their formation. Thus, the studies herein are directly applicable to the understanding and treatment of astrocytomas.