Ganapati Uma, Tan Hongying Tina, Lynch Maureen, Dolezal Milana, de Vos Sven, Gasson Judith C
Division of Hematology-Oncology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA.
Stem Cells. 2007 Aug;25(8):1872-80. doi: 10.1634/stemcells.2006-0547. Epub 2007 Apr 26.
In normal hematopoiesis, proliferation is tightly linked to differentiation in ways that involve cell-cell interaction with stromal elements in the bone marrow stem cell niche. Numerous in vitro and in vivo studies strongly support a role for Notch signaling in the regulation of stem cell renewal and hematopoiesis. Not surprisingly, mutations in the Notch gene have been linked to a number of types of malignancies. To better define the function of Notch in both normal and neoplastic hematopoiesis, a tetracycline-inducible system regulating expression of a ligand-independent, constitutively active form of Notch1 was introduced into murine E14Tg2a embryonic stem cells. During coculture, OP9 stromal cells induce the embryonic stem cells to differentiate first to hemangioblasts and subsequently to hematopoietic stem cells. Our studies indicate that activation of Notch signaling in flk+ hemangioblasts dramatically reduces their survival and proliferative capacity and lowers the levels of hematopoietic stem cell markers CD34 and c-Kit and the myeloid marker CD11b. Global gene expression profiling of day 8 hematopoietic progenitors in the absence and presence of activated Notch yield candidate genes required for normal hematopoietic differentiation, as well as putative downstream targets of oncogenic forms of Notch including the noncanonical Wnts Wnt4 and 5A. Disclosure of potential conflicts of interest is found at the end of this article.
在正常造血过程中，增殖与分化紧密相连，其方式涉及骨髓干细胞龛中与基质成分的细胞间相互作用。大量体外和体内研究有力支持了Notch信号在干细胞更新和造血调控中的作用。毫不奇怪，Notch基因突变与多种类型的恶性肿瘤有关。为了更好地界定Notch在正常和肿瘤性造血中的功能，将一种调节Notch1配体非依赖性、组成型活性形式表达的四环素诱导系统引入小鼠E14Tg2a胚胎干细胞。在共培养过程中，OP9基质细胞诱导胚胎干细胞先分化为成血管细胞，随后分化为造血干细胞。我们的研究表明，flk+成血管细胞中Notch信号的激活显著降低其存活和增殖能力，并降低造血干细胞标志物CD34和c-Kit以及髓系标志物CD11b的水平。在有和没有激活的Notch情况下，对第8天造血祖细胞进行全基因组表达谱分析，得出正常造血分化所需的候选基因，以及Notch致癌形式的推定下游靶点，包括非经典Wnt蛋白Wnt4和5A。潜在利益冲突披露见本文末尾。
