Carlesso N, Aster J C, Sklar J, Scadden D T
Department of Experimental Hematology, Partners AIDS Research Center and MGH Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Blood. 1999 Feb 1;93(3):838-48.
Hematopoiesis is a balance between proliferation and differentiation that may be modulated by environmental signals. Notch receptors and their ligands are highly conserved during evolution and have been shown to regulate cell fate decisions in multiple developmental systems. To assess whether Notch1 signaling may regulate human hematopoiesis to maintain cells in an immature state, we transduced a vesicular stomatitis virus G-protein (VSV-G) pseudo-typed bicistronic murine stem cell virus (MSCV)-based retroviral vector expressing a constitutively active form of Notch1 (ICN) and green fluorescence protein into the differentiation competent HL-60 cell line and primary cord blood-derived CD34(+) cells. In addition, we observed endogenous Notch1 expression on the surface of both HL-60 cells and primary CD34(+) cells, and therefore exposed cells to Notch ligand Jagged2, expressed on NIH3T3 cells. Both ligand-independent and ligand-dependent activation of Notch resulted in delayed acquisition of differentiation markers by HL-60 cells and cord blood CD34(+) cells. In addition, primary CD34(+) cells retained their ability to form immature colonies, colony-forming unit-mix (CFU-mix), whereas control cells lost this capacity. Activation of Notch1 correlated with a decrease in the fraction of HL-60 cells that were in G0/G1 phase before acquisition of a mature cell phenotype. This enhanced progression through G1 was noted despite preservation of the proliferative rate of the cells and the overall length of the cell cycle. These findings show that Notch1 activation delays human hematopoietic differentiation and suggest a link of Notch differentiation effects with altered cell cycle kinetics.
造血作用是增殖与分化之间的一种平衡，这种平衡可能会受到环境信号的调节。Notch受体及其配体在进化过程中高度保守，并且已被证明在多个发育系统中调节细胞命运的决定。为了评估Notch1信号传导是否可能调节人类造血作用以将细胞维持在未成熟状态，我们将一种表达组成型活性形式的Notch1（ICN）和绿色荧光蛋白的水泡性口炎病毒G蛋白（VSV-G）假型双顺反子鼠干细胞病毒（MSCV）基逆转录病毒载体转导到具有分化能力的HL-60细胞系和原代脐血来源的CD34(+)细胞中。此外，我们观察到HL-60细胞和原代CD34(+)细胞表面均有内源性Notch1表达，因此将细胞暴露于在NIH3T3细胞上表达的Notch配体Jagged2。Notch的配体非依赖性和配体依赖性激活均导致HL-60细胞和脐血CD34(+)细胞延迟获得分化标志物。此外，原代CD34(+)细胞保留了形成未成熟集落、混合集落形成单位（CFU-mix）的能力，而对照细胞则丧失了这种能力。Notch1的激活与在获得成熟细胞表型之前处于G0/G1期的HL-60细胞比例的降低相关。尽管细胞的增殖速率和细胞周期的总长度保持不变，但仍注意到通过G1期的进程加快。这些发现表明Notch1激活延迟了人类造血分化，并提示Notch分化效应与改变的细胞周期动力学之间存在联系。
