2013年2月5日，《美国科学院院报》(PNAS)在线发表了同济大学生命科学与技术学院康九红教授研究组关于miR-200/ZEB2在关键转录因子Oct4/Sox2诱导iPSC细胞形成中的重要功能和作用机制的研究成果。该成果是由汪贵英老师和博士生郭旭东共同完成的。
诱导多能干细胞(iPS)技术的创立，为基于干细胞的个性化治疗和再生医学带来光明的前景。因此，Yamanaka教授获得了2012年诺贝尔生理学与医学奖。康九红教授组先前的系列研究显示，miRNAs在Oct4等转录因子诱导iPS细胞形成过程中具有调节p53等信号通路和DNMT3a/3b的重要作用，相关研究发表于2012年的Plos One (7: e40849)、Stem Cells (30: 1645-54) 和2013年的Cell Res (23: 142-56)。
他们发表在PNAS的研究发现，在iPS细胞形成过程中，miR-200家族的miRNAs表达水平呈现逐步升高的趋势。miR-200家族包括5个miRNAs，分别位于染色体Chr.4和Chr.6，形成两个簇，这两个簇如何协同作用是非常有趣的科学问题。汪贵英等的研究发现iPS细胞形成中起关键作用的Oct4和Sox2分别结合到该miRNAs家族簇的两个启动子区域协同激活miR-200s的转录表达，从而在早期阶段有效促进iPS细胞的形成。研究还发现，miR-200直接作用的下游基因是ZEB2，从而也揭示了ZEB2在iPS细胞形成中的新功能。Oct4/Sox2-miR-200-ZEB2通路调节iPS细胞形成的研究成果丰富了人们对iPS细胞形成机制网络的了解。
本研究工作得到科技部973项目、科技部国际合作项目、国家自然科学基金委项目、教育部创新团队以及上海市科委项目等的支持。
doi: 10.1073/pnas.1212769110
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PMID:
Critical regulation of miR-200/ZEB2 pathway in Oct4/Sox2-induced mesenchymal-to-epithelial transition and induced pluripotent stem cell generation
Guiying Wang, Xudong Guo, Wujun Hong, Qidong Liu, Tingyi Wei, Chenqi Lu, Longfei Gao, Dan Yea, Yi Zhou, Jie Chen, Jianmin Wang, Minjuan Wu, Houqi Liu, and Jiuhong Kang
Fibroblasts can be reprogrammed to induced pluripotent stem cells (iPSCs) by application of transcription factors octamer-binding protein 4 (Oct4), SRY-box containing gene 2 (Sox2), Kruppel-like factor 4 (Klf4), and c-Myelocytomatosis oncogene (c-Myc) (OSKM), but the underlying mechanisms remain unclear. Here, we report that exogenous Oct4 and Sox2 can bind at the promoter regions of mir-141/200c and mir-200a/b/429 cluster, respectively, and induce the transcription activation of miR-200 family during the OSKM-induced reprogramming. Functional suppression of miR-200s with specific inhibitors significantly represses the OSKM-caused mesenchymal-to-epithelial transition (MET, an early event in reprogramming of fibroblasts to iPSCs) and iPSC generation, whereas overexpression of miR-200s promotes the MET and iPSC generation. Mechanistic studies showed that miR-200s significantly repress the expression of zinc finger E-box binding homeobox 2 (ZEB2) through directly targeting its 3′ UTR and direct inhibition of ZEB2 can mimic the effects of miR-200s on iPSC generation and MET process. Moreover, the effects of miR-200s during iPSC generation can be blocked by ZEB2 overexpression. Collectively, our findings not only reveal that members of the miR-200 family are unique mediators of the reprogramming factors Oct4/Sox2, but also demonstrate that the miR-200/ZEB2 pathway as one critical mechanism of Oct4/Sox2 to induce somatic cell reprogramming at the early stage.
