Endothelial Cell Role in Yolk Sac Stem Cell Development

我们的工作的总体目标是阐明卵黄囊血岛器官发生的分子机制。这些研究将为血液和内皮细胞发育之间的关系提供新的见解，这些内皮细胞发育是血细胞产生的第一个部位。到目前为止，试剂，以确定卵黄囊造血的最早期事件一直缺乏。我们目前的新的初步数据表明，CD41的表达标志着在小鼠胚胎的原始和永久造血的发病。我们已经利用共聚焦显微镜，以确定原始和永久祖细胞的祖细胞出现的网站，并已开发出一种策略，允许分离的原始红系祖细胞（EryP）从胚胎或胚胎干细胞衍生的胚状体。我们提出3个目标来确定特定分子在血岛器官形成过程中的作用：1。探讨EryP在近端卵黄囊中迁移和扩张的机制。我们推测EryP在近端卵黄囊的迁移和扩张是VEGF依赖性的。2.目的探讨成血管细胞与细胞外基质纤维连接蛋白（Fn）相互作用导致血岛器官形成的机制。我们假设血岛的形成和重塑成毛细血管床是一个Fn依赖的过程，其中成血管细胞迁移通过整合素Fn相互作用，以限制带的原始成红细胞在近端卵黄囊，形成完整的血岛。3.探讨CD41亮细胞簇形成的机制。我们假设CD41亮细胞簇需要Runxl和GATA 2的表达，以从位于远端卵黄囊中的血岛和预先建立的毛细血管（缺乏血细胞）之间的内皮细胞中出现。这些研究将确定血岛发育和重塑所需的分子途径。

The overall goal of our work is to elucidate the molecular mechanisms of yolk sac blood island organogenesis. These studies will provide new insights into the relationship between blood and endothelial cell development in the first site of blood cell production. To date, reagents to identify the earliest events in yolk sac hematopoiesis have been lacking. We present novel preliminary data that CD41 expression marks the onset of primitive and definitive hematopoiesis in the murine embryo. We have utilized confocal microscopy to identify the site of emergence of the progenitor cells of both primitive and definitive progenitors and have developed a strategy that permits isolation of primitive erythroid progenitor cells (EryP) from embryos or embryonic stem cell-derived embryoid bodies. We propose 3 aims to define the roles of specific molecules in the process of blood island organogenesis: 1. To determine the mechanism of EryP migration and expansion in the proximal yolk sac. We hypothesize that EryP migration and expansion in the proximal yolk sac are VEGF dependent. 2. To define the mechanism of angioblast and extracellular matrix fibronectin (Fn) interaction that results in blood island organogenesis. We hypothesize that blood island formation and remodeling into a capillary bed is a Fn dependent process whereby angioblasts migrate via integrin-Fn interactions to circumscribe the band of primitive erythroblasts in the proximal yolk sac to form intact blood islands. 3. To determine the mechanism of CD41 bright cell cluster formation. We hypothesize that CD41 bright cell clusters require the expression of Runxl and GATA2 for emergence from the endothelial cells located between blood islands and pre-established capillaries (devoid of blood cells) in the distal yolk sac. These studies will define molecular pathways required for blood island development and remodeling.