Project description:N6-methyladenosine (m6A) has been recently identified as a conserved epitranscriptomic modification of eukaryotic mRNAs, but its features, regulatory mechanisms, and functions in cell reprogramming are largely unknown. Here, we report m6A modification profiles in the mRNA transcriptomes of four cell types with different degrees of pluripotency. Comparative analysis reveals several features of m6A, especially gene- and cell-type-specific m6A mRNA modifications. We also show that microRNAs (miRNAs) regulate m6A modification via a sequence pairing mechanism. Manipulation of miRNA expression or sequences alters m6A modification levels through modulating the binding of METTL3 methyltransferase to mRNAs containing miRNA targeting sites. Increased m6A abundance promotes the reprogramming of mouse embryonic fibroblasts (MEFs) to pluripotent stem cells; conversely, reduced m6A levels impede reprogramming. Our results therefore uncover a role for miRNAs in regulating m6A formation of mRNAs and provide a foundation for future functional studies of m6A modification in cell reprogramming. m6A-seq in ESC, iPSC, NSC and sertoli cells.
Project description:N6-methyladenosine (m6A) is the most prevalent mRNA modification with diverse regulatory roles in mammalian cells. While its functions are well-documented in mouse embryonic stem cells (mESCs), its role in human pluripotent stem cells (hPSCs) remains to be fully explored. METTL3 is the main enzyme responsible for m6A deposition. Here, using a METTL3 inducible knockout (iKO) system, we uncovered that, unlike in mESCs, METTL3 was indispensable for hPSC maintenance. Importantly, loss of METTL3 caused significant upregulation of pluripotency factors including naïve pluripotency genes and failure to exit pluripotency, thus impaired stem cell differentiation towards embryonic and extraembryonic cells including trophoblasts. Mechanistically, METTL3 iKO in hPSCs substantially increased expression and enhancer activities of two primate-specific transposable elements (TEs), SVA_D and HERVK/LTR5_Hs, which are normally modified by METTL3-dependent m6A. METTL3 loss activated SVA_D by lowering H3K9me3 deposition, and increased chromatin accessibility at LTR5_Hs through the naïve and other pluripotency factors. Conversely, we discovered that the activated SVA_D and LTR5_Hs loci positively regulated naïve gene expression by directly interacted with their promoters. These findings thus reveal that METTL3-dependent m6A RNA methylation has critical roles in suppressing TE expression and in the human pluripotency regulatory network.
Project description:N6-methyladenosine (m6A) has been recently identified as a conserved epitranscriptomic modification of eukaryotic mRNAs, but its features, regulatory mechanisms, and functions in cell reprogramming are largely unknown. Here, we report m6A modification profiles in the mRNA transcriptomes of four cell types with different degrees of pluripotency. Comparative analysis reveals several features of m6A, especially gene- and cell-type-specific m6A mRNA modifications. We also show that microRNAs (miRNAs) regulate m6A modification via a sequence pairing mechanism. Manipulation of miRNA expression or sequences alters m6A modification levels through modulating the binding of METTL3 methyltransferase to mRNAs containing miRNA targeting sites. Increased m6A abundance promotes the reprogramming of mouse embryonic fibroblasts (MEFs) to pluripotent stem cells; conversely, reduced m6A levels impede reprogramming. Our results therefore uncover a role for miRNAs in regulating m6A formation of mRNAs and provide a foundation for future functional studies of m6A modification in cell reprogramming.
