DEVELOPMENTAL HEMATO-ENDOTHELIAL BIOLOGY OF P1H12

内皮细胞（EC）胚胎发育与造血之间的明显联系是发育生物学的一个鲜为人知的基础方面。我们的初步数据表明，p1h12抗原是一种EC-EC粘附分子，在胚胎发生早期表达，可能标志着胚胎细胞具有造血和EC谱系潜力。我们假设P1H12是成血管细胞的标记物，在血管形成的早期阶段发挥作用。我们建议通过解决五个相互关联的具体目标来研究P1H12的生物学。(1)我们将通过鉴定P1H12的结合伙伴和结合域来确定P1H12介导EC-EC粘附的机制。(2)我们将确定P1H12是否为推定成血管细胞的标记物，在体外进行胚胎样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P1H12的小鼠胚胎学表达，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P1H12阳性细胞的分化潜能，使用培养系统确定其谱系生长潜能。(5)我们将定义外周血中发现的P1H12阳性细胞的分化潜力，使用不同的培养系统来定义它们的世系生长潜力。这些研究代表了确定P1H12在胚胎学中的作用的第一步，重点是造血和血管发生（通过令人兴奋的初步数据合理化）。

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).