Coordination of Gene Expression in Retinal Development

描述(由申请人提供)：在整个发育过程中，在成熟的视网膜中，精确控制基因表达对于光感受器的完整性和功能是必不可少的。这包括对时间、地点和表达水平的控制。转录因子提供激活和抑制输入，控制基因表达以响应信号通路。虽然我们对转录激活子的理解已经取得了很大的进展，但我们对参与杆状特异基因精确调控的抑制子的了解仍然很少。这项提议将研究P.I.发现的一种新的抑制物(Fiz1)的作用，该抑制物与杆状分化和杆状特异基因表达的基本激活因子(NRL)有关。 视紫红质基因的严格调控为探索激活因子、抑制因子和信号通路之间的相互作用提供了有用的视紫红质特异基因表达范例。几种转录因子(NRL.NR2E3。CRX)被证明是视紫红质表达的激活剂。这些转录因子的突变会导致视网膜退化。Fiz1是一种锌指蛋白，被发现与NRL结合，并作为视紫红质基因启动子的转录抑制因子。中国人民解放军S实验室最近的研究表明，随着视杆细胞特异性基因表达的开始，视网膜中FIZ1蛋白水平上升。Fiz1还与NR2E3结合，NR2E3是另一种对杆状细胞发育至关重要的转录因子。Fiz1在整个细胞中都可以检测到，并且可以与膜受体酪氨酸激酶(Flt-3)的胞内结构域相互作用。激活这种受体的细胞外蛋白(Flt-3-Ligand，FL)的水平在杆状细胞成熟过程中也会上升。我们假设Fiz1是一种杆状特异基因的转录抑制因子，是响应细胞外信号产生定量精确表达水平所必需的。此外，我们认为Fiz1有助于蛋白质的招募，这些蛋白质调节转录机制对DNA的物理访问。这项建议的具体目标是： 1.确定Fiz1、Flt-3和FL在视网膜发育过程中的表达模式。 2.从视网膜中鉴定Fiz1结合蛋白。 3.检测Fiz1功能突变的获得和丢失对小鼠视杆感光细胞发育的影响。 这些目的将阐明Fiz1在杆状感光受体中的生理作用，并发现杆状特异的转录调控网络的其他组成部分。

DESCRIPTION (provided by applicant): Throughout development, and in the mature retina, precise control of gene expression is essential for photoreceptor integrity and function. This includes control of time, place and level of expression. Transcription factors provide the activation and repression inputs that control gene expression in response to signaling pathways. While much progress has been made towards our understanding of transcriptional activators, our knowledge of the repressors that contribute to the precise regulation of rod-specific genes remains sparse. This proposal will study the role of a novel repressor (Fiz1) that was discovered, by the P.I., from its association with an essential activator (NRL) of rod differentiation and rod-specific gene expression. Stringent regulation of the rhodopsin gene offers a useful paradigm of rod-specific gene expression to explore the interactions between activators, repressors, and signaling pathways. Several transcription factors (NRL. NR2E3. CRX) are shown to be activators of rhodopsin expression. Mutations in these transcription factors cause retinal degeneration. Fiz1 is a zinc-finger protein that was discovered binding to NRL, and behaves as a transcriptional repressor of the rhodopsin gene promoter. Recent studies in the P.l.'s laboratory have shown that Fiz1 protein levels rise in the retina with the onset of rod-specific gene expression. Fiz1 also binds to NR2E3, another transcription factor that is essential for rod development. Fiz1 is detected throughout the cell and can interact with the intracellular domain of a membrane receptor tyrosine-kinase (Flt-3). Levels of the extracellular protein (Flt-3-Ligand, FL) that activates this receptor, also rise during rod-maturation. We hypothesize that Fiz1 is a transcriptional repressor of rod-specific genes and is required for generating quantitatively precise levels of expression in response to extracellular signals. Furthermore, we suggest that Fiz1 assists in the recruitment of proteins that regulate physical access of the transcriptional machinery to DNA. The specific aims of this proposal are: 1. Determine the expression patterns of Fiz1, Flt-3 and FL during retinal development. 2. Identify Fiz1-binding proteins from the retina. 3. Examine the effect of Fiz1 gain and loss of function mutations on mouse rod-photoreceptor development. These aims will elucidate the physiological role of Fiz1 in rod-photoreceptors, and discover additional components of rod-specific transcriptional regulatory networks.