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

描述（由申请人提供）：胶质细胞约占成人中枢神经系统（CNS）细胞群的90%，并支持大量对中枢神经系统功能至关重要的生理作用。然而，体内控制多能神经干细胞胶质细胞形成的分子过程仍然知之甚少。因此，本研究的首要目标是阐明神经干细胞胶质细胞形成的机制。我们最近证明，核因子I （NFI）基因控制胚胎脊髓胶质细胞的产生，并在神经干细胞群体中被诱导，与体内胶质细胞形成的发生一致。这些特性使NFI基因成为研究诱导和维持胶质瘤发生早期阶段的遗传调控程序的理想起点。因此，我们假设解剖与NFI基因调控相关的上游和下游事件将为胶质瘤发生的分子控制提供新的见解。该提案的具体目的1和2是基于我们在胚胎脊髓中发现的两种不同的NFI基因表达调节因子。通过对NFIA启动子的增强子筛选，我们发现了一个高度保守的增强子元件（e123），当引入胚胎鸡脊髓时，它概括了NFIA诱导的空间和时间模式。因此，在Aim 1中，我们建议利用e123作为工具来识别控制NFIA诱导的一组核心转录因子。我们还发现骨形态发生蛋白（BMP）信号以独立于Aim 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Aim 2中，我们计划鉴定NFIA启动子中的BMP应答元件，确定BMP信号在调控NFI基因表达中的具体作用，并确定BMP信号确实独立于调控e123诱导的转录控制机制而运作。最后，Aim 3是神经干细胞基因表达时间谱研究的逻辑延伸，在该研究中，我们确定了胚胎脊髓中NFI基因诱导后上调的一组基因。初步研究表明，在缺乏NFIA的情况下，其中四个基因足以恢复胶质瘤的发生，这表明它们在NFI基因的下游起作用。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细胞形成，以及在胶质细胞形成开始时NFI基因下游的功能。在完成这些研究后，我们期望有一个更全面的分子过程图谱，包括在中枢神经系统发育过程中控制胶质形成起始的NFI基因的上游和下游。由此产生的对神经胶质细胞谱系的信号的深入了解，将把对胚胎脊髓中神经胶质细胞特征的理解从推测领域提升到可以开始考虑临床应用的程度。

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.