The roles of Frizzled-4 and Sox17 in retinal vascular development and maintenance

描述(由申请人提供)：项目摘要：遗传性和获得性视网膜血管疾病是美国失明的主要原因。约翰霍普金斯医学院Jeremy Nathans博士的实验室定义并表征了调节脊椎动物视网膜血管发育的中央信号系统之一--通过Muller胶质细胞衍生配体Norrin的旁分泌作用激活内皮细胞受体Frizzled4(Fz4)和辅助受体LRP5-并描述了这一途径的干扰如何导致人类一系列遗传性视网膜血管疾病。我们实验室最近的发现表明，Fz4是一种泛内皮细胞受体，在成年小鼠的成熟视网膜血管中继续表达，这表明Fz4功能可能是维持成熟血管或如何应对缺血性视网膜病变所必需的。此外，我们还鉴定了一个转录因子Sox17，它似乎是Norrin/Fz4信号在发育中的视网膜血管系统中的下游效应因子。这项培训由两个目标组成，第一个目标是利用条件FZ4小鼠在成熟的视网膜血管中表征FZ4的体内功能，这些小鼠只有在成年血管神经丛完全发育后才能操纵FZ4信号。利用这些小鼠，我们还将通过表征激光诱导的视网膜动脉和静脉阻塞导致的新生血管生长的模式和时间过程，来研究Fz4在缺血性视网膜病变中的作用。第二个目的是利用条件靶向的Sox17小鼠，通过Cre介导的重组，允许基因失活，特别是在内皮细胞中，来表征Sox17在视网膜血管发育中的体内功能。为了帮助促进这些研究，我们正在建立小鼠系，使我们能够荧光标记肌动蛋白细胞骨架和视网膜内皮细胞的特定亚群。总之，这些目标将为了解Norrin/Fz4信号通路在血管健康中的功能提供重要的洞察力，长期目标是开发先天性和获得性视网膜血管疾病的创新医疗方法。

DESCRIPTION (provided by applicant): Project Summary: Inherited and acquired retinal vascular disorders are a leading cause of blindness in the United States. The laboratory of Dr. Jeremy Nathans at Johns Hopkins Medical School has defined and characterized one of the central signaling systems that regulates vascular development in the vertebrate retina-the activation of the endothelial cell receptor Frizzled4 (Fz4) and coreceptor Lrp5 by the paracrine action of the Muller glia-derived ligand Norrin-and described how perturbations in this pathway cause a series of inherited retinal vascular disorders in humans. Recent findings from our lab now indicate that Fz4 is a pan-endothelial receptor that continues to be expressed in the mature retinal blood vessels of adult mice, suggesting that Fz4 functions may be required for the maintenance of mature blood vessels or how they respond to ischemic retinopathy. Also, we have identified a transcription factor, Sox17, which appears to be a downstream effector of Norrin/Fz4 signaling in the developing retinal vasculature. This training fellowship consists of two aims, the first of which proposes to characterize the in vivo functions of Fz4 in mature retinal blood vessels using conditional Fz4 mice that permit the manipulation of Fz4 signaling only after the adult vascular plexus has fully developed. Using these mice, we will also investigate the functions of Fz4 in ischemic retinopathy by characterizing the pattern and time course of new blood vessel growth in response to laser-induced retinal artery and vein occlusion. The second aim proposes to characterize the in vivo functions of Sox17 in retinal vascular development using conditionally targeted Sox17 mice that permit gene inactivation, via Cre-mediated recombination, specifically in endothelial cells. To help facilitate these studies, we are generating mouse lines that will enable us to fluorescently label the actin cytoskeleton and specific subpopulations of retinal endothelial cells. Together, these aims will provide important insight into the functions of the Norrin/Fz4 signaling pathway in vascular health, with the long term goals of developing innovative medical treatments for congenital and acquired retinal vascular disorders.