Development of high-level expression vectors in embryonic and hematopoietic stem cells and generati of GM-CSF and IL-3 of receptor transgenic mice

产生表达人GM-CSF（hGM-CSF）高亲和力受体的转基因小鼠。受体的表达受H-2L-d I类启动子的控制，导致其在许多造血细胞（包括脾细胞、胸腺细胞和骨髓细胞）上表达。小鼠GM-CSF（mGM-CSF）不与人受体结合，因此hGM-CSF受体（hGMR）转基因小鼠在缺乏外源性hGM-CSF的情况下表现出正常的表型，在甲基纤维素集落试验中检测hGMR转基因小鼠的骨髓造血祖细胞，加入hGM-CSF导致多谱系集落的形成，包括红细胞集落，其生成通常依赖于促红细胞生成素。在mGM-CSF存在下，仅产生粒细胞和巨噬细胞集落。这些数据表明，各种髓系祖细胞的细胞因子反应性是在受体表达水平上调节的，而不是通过下游信号转导机制。我们还研究了hGM-CSF信号转导对hGMR转基因小鼠胸腺细胞分化的影响。hGM-CSF可将增殖信号传递给表达hGMR的胸腺细胞亚群，而胸腺细胞对mGM-CSF无反应。将hGM-CSF体内施用到hGMR小鼠中还显示，hGM-CSF支持髓系细胞增殖和分化，但抑制胸腺细胞分化。

Transgenic mice expressing the human GM-CSF (hGM-CSF) high affinity receptor were generated. Expression of the receptor is under control of the H-2L^d class I promoter, resulting in its expression on numerous hematopoietic cells, including splenocytes, thymocytes, and bone marrow cells. Murine GM-CSF (mGM-CSF) does not bind to the human receptor, therefore hGM-CSF receptor(hGMR)transgenic mice display normal phenotypes in the absence of exogenous hGM-CSF.In methylcellulose colony assays which examine bone marrow hematopoietic progenitors from hGMR transgenic mice, addition of hGM-CSF lead to the formation of multiple lineage colonies, including erythrocyte colonies whose genration normally depends on erythropoietin. In the presence of mGM-CSF,only granulocyte and macrophage colonies were generated. These data suggest that cytokine responsiveness of various myeloid progenitors is regulated at the level of receptor expression rather than through downstream signal transduction machinery. We also examined effects of hGM-CSF signalling on the differentiation of thymocytes from hGMR transgenic mice. hGM-CSF can transduce proliferation signals to thymic subsets when they express hGMR,while thymocytes does not respond to mGM-CSF.Addition of hGM-CSF to fetal thymic organ cultures inhibited thymocyte differentiation in stage-specific manner. In vivo administration of hGM-CSF into hGMR mice also showed that hGM-CSF supports myeloid lineage cell proliferation and differentiation but inhibits thymocyte differentiation.