METTL1-mediated m7G methylation maintains pluripotency in human stem cells and limits mesoderm differentiation and vascular development

Abstract

Background: 7-Methylguanosine (m 7 G) is one of the most conserved modifications in nucleosides within tRNAs and rRNAs. It plays essential roles in the regulation of mRNA export, splicing, and translation. Recent studies highlighted the importance of METTL1-mediated m 7 G tRNA methylome in the self-renewal of mouse embryonic stem cells (mESCs) through its ability to regulate mRNA translation. However, the exact mechanisms by which METT L1 regulates pluripotency and differentiation in human induced pluripotent stem cells (hiPSCs) remain unknown. In this study, we evaluated the functions and underlying molecular mechanisms of METTL1 in regulating hiPSC selfrenewal and differentiation in vivo and in vitro. Methods: By establishing METTL1 knockdown (KD) hiPSCs, gene expression profiling was performed by RNA sequencing followed by pathway analyses. Anti-m 7 G northwestern assay was used to identify m 7 G modifications in tRNAs and mRNAs. Polysome profiling was used to assess the translation efficiency of the major pluripotent transcription factors. Moreover, the in vitro and in vivo differentiation capacities of METTL1-KD hiPSCs were assessed in embryoid body (EB) formation and teratoma formation assays. Results: METTL1 silencing resulted in alterations in the global m 7 G profile in hiPSCs and reduced the translational efficiency of stem cell marker genes. METTL1-KD hiPSCs exhibited reduced pluripotency with slower cell cycling. Moreover, METTL1 silencing accelerates hiPSC differentiation into EBs and promotes the expression of mesodermrelated genes. Similarly, METTL1 knockdown enhances teratoma formation and mesoderm differentiation in vivo by promoting cell proliferation and angiogenesis in nude mice. Conclusion: Our findings provided novel insight into the critical role of METTL1-mediated m 7 G modification in the regulation of hiPSC pluripotency and differentiation, as well as its potential roles in vascular development and the treatment of vascular diseases.

RNA nucleotide methylation: 2021 update

“…The tRNA m 7 G46 modification is mediated by TrmB in bacteria and the heterodimeric complexes Trm8/Trm82 (METTL1/WDR4) in yeast and human, respectively. Correct m 7 G46 methylation is required for maintenance of mRNA translation and embryonic stem cell self-renewal and differentiation (Deng et al, 2020;Lin et al, 2018). Deficient tRNA m 7 G46 modification is a cause of microcephalic primordial dwarfism (Filonava et al, 2015;Shaheen et al, 2015) and is also involved in sensitivity of cancer cells to 5-fluorouracil (Okamoto et al, 2014).…”

Epigenetics: Roles and therapeutic implications of non-coding RNA modifications in human cancers

“… 64 METTL1-WDR4, i.e., a tRNA m7G methyltransferase complex, sets up a subset of internal m7G in mRNA. 65 Nuclear paraspeckle assembling transcript 1 (NEAT1) refers to a lncRNA as one vital subnuclear paraspeckle body structure. In the two isoforms (NEAT1_1 and NEAT1_2) under the generation from the processing of alternative 3′ end RNA, NEAT1_2, which is longer, is critical to the paraspeckle forming process ( Figure 3 ).…”

m7G Methyltransferase METTL1 Promotes Post-ischemic Angiogenesis via Promoting VEGFA mRNA Translation

“…Mouse embryonic stem cells lacking METTL1 or WDR4 display defects in self-renewal and neural differentiation (Lin et al, 2018). METTL1-mediated m7G methylation could also regulate the pluripotency and differentiation of human-induced pluripotent stem cells, thus suggesting its potential roles in vasculogenesis and the treatment of vascular diseases (Deng et al, 2020). Nevertheless, the evidence for crucial signaling between the relevant catalases linking m7G and angiogenesis remains unclear.…”