Tet and TDG Mediate DNA Demethylation Essential for Mesenchymal-to-Epithelial Transition in Somatic Cell Reprogramming

• Published in: Cell stem cell Vol. 14; no. 4; pp. 512 - 522
• Main Authors: Hu, Xiao, Zhang, Lei, Mao, Shi-Qing, Li, Zheng, Chen, Jiekai, Zhang, Run-Rui, Wu, Hai-Ping, Gao, Juan, Guo, Fan, Liu, Wei, Xu, Gui-Fang, Dai, Hai-Qiang, Shi, Yujiang Geno, Li, Xianlong, Hu, Boqiang, Tang, Fuchou, Pei, Duanqing, Xu, Guo-Liang
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03.04.2014
• Subjects: Animals; Blotting, Western; Cell Differentiation; Cell Lineage; Cells, Cultured; Cellular Reprogramming; DNA Glycosylases - physiology; DNA Methylation; DNA-Binding Proteins - physiology; Embryo, Mammalian - cytology; Embryo, Mammalian - metabolism; Embryonic Stem Cells - cytology; Embryonic Stem Cells - metabolism; Epigenesis, Genetic; Epithelial-Mesenchymal Transition; Fibroblasts - cytology; Fibroblasts - metabolism; Flow Cytometry; Gene Expression Regulation; Immunoenzyme Techniques; Induced Pluripotent Stem Cells - cytology; Induced Pluripotent Stem Cells - metabolism; Mice; Mice, Knockout; MicroRNAs - physiology; Proto-Oncogene Proteins - physiology; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics
• ISSN: 1934-5909; 1875-9777; 1875-9777
• DOI: 10.1016/j.stem.2014.01.001

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. [Display omitted] •Tet dioxygenases and TDG glycosylase are essential for fibroblast reprogramming•Tet and TDG mediate demethylation and reactivation of miRNAs critical for MET•Tet enzymes are not required for the reactivation of pluripotency loci Using triple Tet gene knockout cells, Hu et al. show that Tet activity is required for reprogramming of fibroblasts to iPSCs for activation of key miRNA expression during the MET step.