DEVELOPMENTAL HEMATO-ENDOTHELIAL BIOLOGY OF P1H12

内皮细胞(EC)胚胎发育和造血之间的明显联系是发育生物学中一个知之甚少但又基本的方面。我们的初步数据表明，P1H12-抗原是一种EC-EC黏附分子，在胚胎发育早期就表达，可能标志着胚胎细胞同时具有造血和EC血统。我们推测，P1H12是血管母细胞的标志物，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特定目标来研究P1H12的生物学。(1)我们将通过确定P1H12的S结合伙伴和结合结构域来确定P1H12介导EC-EC黏附的机制。(2)我们将确定P1H12是否是可能的血管母细胞的标志，并在体外进行类胚体分化研究和小鼠胚胎的传代潜能研究。(3)我们将利用标准的组织学、免疫组织化学和原位杂交技术，记录P1H12在小鼠胚胎中的表达，并确定其缺失的表型。(4)确定成人骨髓中发现的P1H12‘S阳性细胞的分化潜能，利用培养体系确定其向外生长的潜能。(5)我们将确定外周血中发现的P1H12阳性细胞的分化潜能，并使用不同的培养系统来确定它们的谱系分化潜能。这些研究代表了确定P1H12在胚胎学中的作用的第一步，重点是造血和血管生成(通过令人兴奋的初步数据进行合理化)。

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).