Shanghai Key Laboratory of Molecular Andrology, The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
CAS Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.
Cell Stem Cell. 2014 Apr 3;14(4):512-22. doi: 10.1016/j.stem.2014.01.001. Epub 2014 Feb 13.
Tet-mediated DNA oxidation is a recently identified mammalian epigenetic modification, and its functional role in cell-fate transitions remains poorly understood. Here, we derive mouse embryonic fibroblasts (MEFs) deleted in all three Tet genes and examine their capacity for reprogramming into induced pluripotent stem cells (iPSCs). We show that Tet-deficient MEFs cannot be reprogrammed because of a block in the mesenchymal-to-epithelial transition (MET) step. Reprogramming of MEFs deficient in TDG is similarly impaired. The block in reprogramming is caused at least in part by defective activation of key miRNAs, which depends on oxidative demethylation promoted by Tet and TDG. Reintroduction of either the affected miRNAs or catalytically active Tet and TDG restores reprogramming in the knockout MEFs. Thus, oxidative demethylation to promote gene activation appears to be functionally required for reprogramming of fibroblasts to pluripotency. These findings provide mechanistic insight into the role of epigenetic barriers in cell-lineage conversion.
Tet 介导的 DNA 氧化是最近发现的哺乳动物表观遗传修饰，其在细胞命运转变中的功能作用仍知之甚少。在这里，我们获得了三种 Tet 基因均缺失的小鼠胚胎成纤维细胞（MEFs），并研究了它们重编程为诱导多能干细胞（iPSCs）的能力。我们发现 Tet 缺陷型 MEFs 由于间充质向上皮转化（MET）步骤的阻断而无法被重编程。TDG 缺陷的 MEFs 的重编程也受到类似的阻碍。重编程的阻断至少部分是由于关键 miRNA 的激活缺陷所致，这依赖于 Tet 和 TDG 促进的氧化去甲基化。受影响的 miRNA 或催化活性 Tet 和 TDG 的重新引入可恢复敲除 MEFs 中的重编程。因此，促进基因激活的氧化去甲基化似乎是将成纤维细胞重编程为多能性所必需的功能。这些发现为表观遗传障碍在细胞谱系转换中的作用提供了机制上的见解。
