Coordination of Gene Expression in Retinal Development

描述（由申请人提供）：在整个发育过程中，以及在成熟的视网膜中，精确控制基因表达对于光感受器的完整性和功能至关重要。这包括控制表达的时间、地点和层次。转录因子提供激活和抑制输入，控制基因表达响应信号传导途径。虽然我们对转录激活因子的理解已经取得了很大的进展，但我们对抑制因子的知识仍然很少，这些抑制因子有助于杆特异性基因的精确调控。这项提议将研究一种新的阻遏物（Fiz 1）的作用，这种阻遏物是由P.I.发现的，从其与视杆细胞分化和视杆细胞特异性基因表达的必需激活因子（NRL）的相关性。 视紫红质基因的严格调控为研究视杆细胞特异性基因表达提供了一个有用的范例，以探索激活子、抑制子和信号通路之间的相互作用。几种转录因子（NRL. NR2E3。CRX）显示为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变性。Fiz 1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。最近的研究在P.L.的实验室已经表明，随着视杆细胞特异性基因表达的开始，视网膜中的Fiz 1蛋白水平上升。Fiz 1还与NR 2 E3结合，NR 2 E3是另一种对视杆发育至关重要的转录因子。Fiz 1在整个细胞中被检测到，并且可以与膜受体酪氨酸激酶（Flt-3）的细胞内结构域相互作用。激活该受体的细胞外蛋白（Flt-3-配体，FL）的水平也在视杆成熟期间升高。我们假设，Fiz 1是一个杆特异性基因的转录抑制因子，并需要产生定量精确的表达水平响应细胞外信号。此外，我们认为，Fiz 1有助于招聘的蛋白质，调节物理访问的转录机器的DNA。这项建议的具体目标是： 1.确定Fiz 1、Flt-3和FL在视网膜发育过程中的表达模式。 2.识别视网膜中的Fiz 1结合蛋白。 3.检查Fiz 1功能突变的获得和丧失对小鼠视杆细胞发育的影响。 这些目标将阐明Fiz 1在视杆光感受器中的生理作用，并发现视杆特异性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.