Role of typeIII receptor tyrosine kinases in lympho-hematopoietic tissues

这项资助涵盖了三个项目，以了解胚胎中淋巴造血组织发育的分子机制。以下是我们的进展摘要。1)我们试图定义造血细胞和血管内皮细胞分化途径的所有中间阶段。为此，我们开发了识别pdgfrα， c-Kit和Flkl的单克隆抗体，这些单克隆抗体表达小鼠胚胎新生中胚层的不同亚群。这些表面标记物与E-cadherin、V-cadherin、CD34、CD31和CD45结合，成功地定义了所有可能的中间阶段。我们目前正在研究调节这一分化途径中每个分支点的分子机制。2)研究了peyer斑块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 patch形成的分子要求，但尚不清楚这些分子如淋巴毒素如何参与peyer's patch analage的形成。使用IL-7Ralpha- ko小鼠和拮抗IL-7Ralpha- mab，我们发现IL-7Ralpha^+未成熟淋巴细胞是表皮斑块的诱导因子。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缺乏peyer补丁但其他方面正常的小鼠。该模型有助于了解peyer’s patch在粘膜免疫中的作用。3)为了了解造血微环境的发展，我们发现pdgfrα在与造血细胞相关的胎肝基质细胞成分中表达。使用缺乏pdgfrα分子的Ph/Ph突变小鼠，我们发现在缺乏pdgfrα的情况下不会启动成体型红细胞生成。

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.