Identification of genes which are involved in the development and transdifferentiation of hematopoietic stem cells

在这项研究中，我们试图阐明小鼠胚胎AGM区是如何发育出造血干细胞的，以及哪些因素参与了骨髓干细胞向受损器官的募集。首先，我们鉴定了一组基因，这些基因在纯化的骨髓来源的造血干细胞中表达，而在分化的ES细胞来源的血管母细胞中不表达。它们包括SHP1、c-MPL、NOREL和未知基因S76。S76基因主要在成年小鼠的造血组织中表达，并编码一种膜蛋白。RNAi介导的S76基因在造血祖细胞中的表达抑制了造血祖细胞的生长，并增强了肥大细胞的增殖能力，提示S76可能是一种新的血细胞因子反应性调节因子。另一方面，我们发现了一种新的蛋白水解酶RAMP和趋化因子Bray，这两种蛋白在肌营养不良症突变小鼠MDX中都有上调。RAMP和Brak在骨骼肌和脑中表达，并参与肌肉再生过程。为了阐明这些分泌蛋白在体内的作用，我们新建立了转基因和基因敲除小鼠品系。除了上述研究外，我们还发现了Meis3和RUNX1的新功能，并对自然重塑组织卵巢和子宫进行了基因图谱研究。尽管我们只获得了线索，但未来利用转基因小鼠进行的研究将为造血干细胞的开发和转分化提供一个新的范式。

In this investigation, we attempted to elucidate how hematopoietic stem cells are developed from AGM region of mouse embryos, and which factors are involved in the recruitment of bone marrow stem cells to injured organs First, we identified a set of genes which are expressed in purified bone marrow-derived hematopoietic stem cells, but not in hemangioblasts derived from differentiated ES cells. They included SHP1, c-mpl, Norel, and unknown gene S76. S76 mRNA is predominantly expressed in hematopoietic tissues in adult mice and encoded a membrane protein. RNAi mediated r repression of S76 mRNA in hematopoietic progenitor cells inhibited their growth, and augmented proliferative capacity of mast cell line, suggesting that S76 could be a novel regulator of cytokine-responsiveness in blood cells. On the other hand, we identified a novel protease RAMP and chemokine BRAY, both of which are up-regulated in muscular dystrophy mutant mice, mdx. RAMP and BRAK are expressed in skeletal muscle and brain, and associated in the process of muscle regeneration. In order to clarify in vivo roles of these secreted proteins, we newly generated transgenic and knock-out mouse lines. In addition to above described researches, we discovered novel roles of Meis3 and Runx1, and performed gene profiling studies of ovary and uterus, naturally-remodeling tissues. Although we only obtained clues, future studies by using genetically modified mice would provide a new paradigm for the development and transdifferentiation of hematopoietic stem cells.