Roles for c-Myc in self-renewal of hematopoietic stem cells
Roles for c-Myc in self-renewal of hematopoietic stem cells
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DOI：
10.1074/jbc.m400407200
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发表时间：
2004-06-11
影响因子：
4.8
通讯作者：
Kanakura, Y
中科院分区：
文献类型：
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作者：
Satoh, Y;Matsumura, I;Kanakura, Y
Notch和HOXB 4已被报道在体外扩增造血干细胞（HSC）。然而，它们的关键效应分子仍然没有确定。我们发现，c-myc，细胞周期蛋白D2，细胞周期蛋白D3，细胞周期蛋白E，和E2 F1的表达诱导或增强在Notch 1或HOXB 4诱导的小鼠HSC的自我更新。由于c-Myc可以作为G（1）/S转换的主要调节因子，我们研究了c-Myc单独是否可以诱导HSC的自我更新。在与干细胞因子、FLT 3配体和IL-6的培养中，4-羟基他莫昔芬诱导形式的c-Myc（Myc/ERT）使鼠Lin（-）Sca-1（+）HSC能够以与HSC相容的表面表型增殖超过28天。4-羟基他莫昔芬激活的c-Myc增强了端粒酶活性，在集落测定中使CFU-Mix的数量增加了约2倍。此外，在重建试验中，c-Myc扩增的HSC可以重建造血超过6个月。对于Notch 1诱导c-myc的机制，我们发现Notch 1的激活形式（NotchIC）及其下游效应重组信号结合蛋白-J κ（RBP-VP 16）可以通过诱导DNA结合复合物激活c-myc启动子-195 bp ~-161 bp之间的元件。总之，这些结果表明c-Myc可以作为Notch和HOXB 4的下游介质支持HSC的自我更新。
Notch and HOXB4 have been reported to expand hematopoietic stem cells (HSCs) in vitro. However, their critical effector molecules remain undetermined. We found that the expression of c-myc, cyclin D2, cyclin D3, cyclin E, and E2F1 was induced or enhanced during Notch1- or HOXB4-induced self-renewal of murine HSCs. Since c-Myc can act as a primary regulator of G(1)/S transition, we examined whether c-Myc alone can induce self-renewal of HSCs. In culture with stem cell factor, FLT3 ligand, and IL-6, a 4-hydroxytamoxifen-inducible form of c-Myc (Myc/ERT) enabled murine Lin(-) Sca-1(+) HSCs to proliferate with the surface phenotype compatible with HSCs for more than 28 days. c-Myc activated by 4-hydroxytamoxifen augmented telomerase activities and increased the number of CFU-Mix about 2-fold in colony assays. Also, in reconstitution assays, HSCs expanded by c-Myc could reconstitute hematopoiesis for more than 6 months. As for the mechanism of c-myc induction by Notch1, we found that activated forms of Notch1 (NotchIC) and its downstream effector recombination signal-binding protein-J kappa (RBP-VP16) can activate the c-myc promoter through the element between -195 bp and -161 bp by inducing the DNA-binding complex. Together, these results suggest that c-Myc can support self-renewal of HSCs as a downstream mediator of Notch and HOXB4.