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之间的关系提供新的见解。迄今为止，确定卵黄囊造血最早事件的试剂一直缺乏。我们提出了新的初步数据，CD41的表达标志着小鼠胚胎中原始和最终造血的开始。我们利用共聚焦显微镜来确定原始祖细胞和终祖细胞的祖细胞出现的位置，并开发了一种策略，允许从胚胎或胚胎干细胞衍生的胚状体中分离原始红系祖细胞（EryP）。我们提出3个目标来定义特定分子在血岛器官发生过程中的作用：1。探讨EryP在卵黄囊近端迁移扩张的机制。我们假设卵黄囊近端EryP的迁移和扩张依赖于VEGF。2. 明确成血管细胞和细胞外基质纤维连接蛋白相互作用导致血岛器官发生的机制。我们假设血岛的形成和毛细血管床的重塑是一个依赖于Fn的过程，在这个过程中，成血管细胞通过整合素-Fn相互作用迁移到卵黄囊近端原始红母细胞带，形成完整的血岛。3. 探讨CD41明亮细胞簇形成的机制。我们假设CD41亮细胞簇需要Runxl和GATA2的表达才能从位于远端卵黄囊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.