DEVELOPMENTAL HEMATO-ENDOTHELIAL BIOLOGY OF P1H12

内皮细胞（EC）的胚胎发育和造血之间的明显联系是发育生物学的一个基本方面，但知之甚少。 我们的初步数据表明，P1 H12抗原是一种EC-EC粘附分子，在胚胎发生的极早期表达，并可能标志着胚胎细胞具有造血和EC谱系潜力。 我们假设P1 H12是成血管细胞的标志物，在血管发生的最早阶段起作用。 我们建议通过解决五个相互关联的具体目标来研究P1 H12的生物学。 (1)我们将通过鉴定P1 H12的结合伴侣和结合结构域来确定P1 H12介导EC-EC粘附的机制。 (2)我们将确定P1 H12是否是假定的成血管细胞的标志物，进行体外胚状体的分化研究和小鼠胚胎的谱系潜力研究。(3)我们将使用标准的组织学、免疫组织化学和原位杂交技术，记录P1 H12在小鼠胚胎中的表达，并确定其缺失表达的表型。 (4)我们将定义成人骨髓中发现的P1 H12阳性细胞的分化潜力，使用培养系统来确定其谱系生长潜力。(5)我们将使用各种培养系统来确定外周血中发现的P1 H12阳性细胞的分化潜力，以确定其谱系生长潜力。 这些研究代表了定义P1 H12在胚胎学中作用的第一步，重点是造血和血管发生（令人兴奋的初步数据证明了这一点）。

The apparent linkage between embryologic development of endothelial cells (EC) and hematopoiesis is a poorly understood but fundamental aspect of developmental biology. Our preliminary data indicate that P1H12-antigen is an EC-EC adhesion molecule, is expressed extremely early in embryogenesis, and probably marks embryonic cells having both hematopoietic and EC lineage potential. We hypothesize that P1H12 is a marker of the hemangioblast and plays a role in the earliest stages of vasculogenesis. We propose to study the biology of P1H12 by addressing five interrelated specific aims. (1) We will identify the mechanism by which P1H12 mediates EC-EC adhesion by identifying P1H12's binding partner and binding domains. (2) We will determine whether P1H12 is a marker of the putative hemangioblast, conducting differentiation studies in embryoid bodies in vitro and lineage-potential studies in murine embryos. (3) We will document the murine embryologic expression of P1H12 and define the phenotype of its absent expression, using standard techniques of histology, immuno-histochemistry, and in situ hybridization. (4) We will define the differentiation potential of P1H12's positive cells found in adult bone marrow, using culture systems to determine their lineage outgrowth potential. (5) We will define the differentiation potential of P1H12 positive cells found in peripheral blood, using various culture systems to define their lineage-outgrowth potential. These studies represent a first step towards defining the role of P1H12 in embryology, with an emphasis on hematopoiesis and vasculogenesis (as rationalized by exciting preliminary data).