DERIVATION OF MODEL SYSTEMS FOR HEMATOPOIETIC GROWTH FACTOR RECEPTOR FUNCTION

造血生长因子(HGF)受体是血管生成的第一环。 最终导致细胞增殖或分化的信号的传递 造血祖细胞。信号转导的最新进展 提示大多数受体与重叠的几组 细胞内的次级效应器。因此，值得注意的是 看似相反的反应--增殖和分化--可能是 通过共同的效应器蛋白发出信号，而这种特异性在 可以维持对给定HGF的反应。实现这一目标的方法是 未知。将开发两个模型系统来解决这些问题。 在第一个模型中，将使用大鼠嗜铬细胞瘤细胞系PC12 目的：研究小鼠白细胞介素3受体(IL-3R)的功能。 初步数据表明，IL-3R组件被引入到 PC12细胞，IL-3刺激可诱导神经元分化。 因此，IL-3R的结构-功能关系和其他因子的作用 肝细胞生长因子和肝细胞生长因子嵌合受体可以在缺乏 干扰内源性受体，并在分化的背景下 而不是扩散。嵌合受体已被用来确定 人绒毛膜促性腺激素受体的关键区介导的特异性 分化反应。例如，EPO-R/BetaIL-3R嵌合体 受体可以诱导祖细胞系有限的分化， 即使它缺少EPO-R的细胞质区域。一种潜力 在这些实验中需要注意的是，指示细胞系 只允许有限的差异化，而且可能已经 预先忠于某一特定血统的。因此，观察到的差异可以 不能反映生理反应。为了绕过这一限制并 解决特异性问题，胚胎干细胞克隆将 获得了野生型促红细胞生成素(EPO)受体 被EPO-R/β-IL-3R嵌合受体取代。这一点的贡献 嵌合受体促进造血，更具体地说 将在体内监测纯合子小鼠的红细胞生成情况 嵌合受体，并在体外与祖细胞进行克隆试验 起源于类胚体。上面描述的这两个模型系统 提出了一种新的检测HGF-R功能的方法，并补充或 改进主要依赖扩散的现有模式。

Hematopoietic growth factor (HGF) receptors are the first link in the relay of signals that culminate in proliferation or differentiation of a progenitor hematopoietic cell. Recent advances in signal transduction suggest that the majority of receptors interact with overlapping sets of secondary effectors inside the cell. It is therefore remarkable that seemingly opposite responses -proliferation and differentiation- can be signaled through shared effector proteins, and that specificity in response to a given HGF can be maintained. How this is achieved is unknown. Two model systems will be developed to address these questions. In the first model, the rat pheochromocytoma cell line PC12 will be used to study the function of the mouse interleukin-3 receptor (IL-3R). Preliminary data suggest that introduction of the IL-3R components into PC12 cells, and stimulation with IL-3 leads to neuronal differentiation. Thus, structure-function relationship of the IL-3R and the role of other HGF and HGF chimeric receptors can be assessed in the absence of interfering endogenous receptors, and in the context of differentiation rather than proliferation. Chimeric receptors have been used to define critical regions in HCF receptors mediating specificity in the differentiation response. For instance, an EPO-R/betaIL-3R chimeric receptor can induce limited differentiation of a progenitor cell line, even though it lacks the cytoplasmic region of the EPO-R. One potential caveat in these experiments is the fact that the indicator cell line is only permissive to limited differentiation, and may already be precommitted to a given lineage. Thus, the observed differentiation may not reflect a physiological response. To circumvent this limitation and address the question of specificity, embryonic stem (ES) cell clones will be obtained in which the wild-type erythropoietin (EPO) receptor has been replaced by an EPO-R/betaIL-3R chimeric receptor. The contribution of this chimeric receptor to blood formation and more specifically to erythropoiesis will be monitored in vivo in mice homozygous for the chimeric receptor, and, in vitro, in colony assay with progenitor cells derived from embryoid bodies. These two model systems described above represent a novel approach to assay HGF-R function, and complement or improve existing models that rely primarily on proliferation.