Role of typeIII receptor tyrosine kinases in lympho-hematopoietic tissues

这笔赠款包括三个项目，以了解胚胎淋巴造血组织发育的分子机制。以下是我们进展的总结。1)我们试图定义向造血细胞和血管内皮细胞分化的所有中间阶段。为此，我们研制了识别PDGFRα、c-Kit和Flk1的单抗，它们是小鼠胚胎新生中胚层的不同亚群。这些表面标志物与E-钙粘蛋白、V-钙粘蛋白、CD34、CD31和CD45一起成功地确定了可能所有可能的中期。我们目前正在研究调控这一分化途径中每个分支点的分子机制。2)研究了Peyer氏斑形成的细胞和分子基础。虽然通过对各种KO小鼠的分析已经阐明了Peyer‘s斑块形成的分子要求，但这些分子，如淋巴毒素如何参与Peyer’s斑块类似物的形成尚不清楚。用IL-7Rα-KO小鼠和一种拮抗剂抗IL-7Rα-mAb，我们发现IL-7Rα~+未成熟淋巴细胞是Peyer‘s斑块原基的诱导者。本研究首次证明了未成熟淋巴细胞有其独特的功能。基于这一发现，我们成功地培育出了没有佩尔氏斑但其他方面正常的小鼠。该模型小鼠将有助于了解Peyer氏斑在黏膜免疫中的作用。3)为了了解造血微环境的发展，我们发现PDGFRpha在胎肝基质细胞成分中表达，与造血细胞相关。使用缺乏这种分子的Ph/Ph突变小鼠，我们发现在缺乏PDGFRpha的情况下，成人型红细胞转化不会启动。

This grant covered three projects to understand the molecular mechanisms underlying development of lymphohematopoietic tissues in the embryo. Followings are the summary of our progress.1) We attempted to define all intermediate stages in the differentiation pathway towards hematopoietic and vascular endothelial cells. For this purpose, we developed mAbs recognizing PDGFRalpha, c-Kit and Flkl that are expressed distinct subsets of nascent mesoderm of mouse embryo. These surface markers in combination with E-cadherin, V-cadherin, CD34, CD31 and CD45 were successfully used to define probably all possible intermediate stages. We are currently investigating the molecular mechanisms regulating each branching point in this differentiation pathway.2) Cellular and molecular basis for peyer's patch formation was investigated. While molecular requirements for peyer's patch formation has been elucidated through the analysis of various KO mice, it has been unclear how these molecules like lymphotoxins are involved in the formation of peyer's patch analage. Using IL-7Ralpha-KO mice and an antagonistic anti-IL-7Ralpha-mAb, we found that IL-7Ralpha^+ immature lymphocytes are the inducer of the peyer's patch anlage. This study demonstrated for the first time that immature lymphocyte has its own unique function. Based on this finding, we succeeded to produce mice that lacks peyer's patch but otherwise normal. This model mice will be helpful to understand the role of peyer's patch in the mucosal immunity.3) In an attempt to understand the development of hematopoietic microenvironment, we found that PDGFRalpha is expressed in the stromal cell component of the fetal liver on which hematopoietic cells are associated. Using Ph/Ph mutant mice that lacks this molecule, we found that adult-type erythropoesis was not initiated in the absence of PDGFRalpha.