DUX-miR-344-ZMYM2-mediated activation of MERVL LTRs induces a totipotent 2C-like state [RNA-seq]

Mouse embryonic stem cells (ESCs) sporadically express preimplantation two-cell-stage (2C) transcripts, including MERVL endogenous retrovirus and Zscan4 cluster genes. Such 2C-like cells (2CLCs) can contribute to both embryonic and extraembryonic tissues when reintroduced into early embryos. We examined global nucleosome occupancy and gene expression in 2CLCs and identified miR-344 as the noncoding molecule that positively controls 2CLC potency. We found that activation of endogenous MERVL or miR-344-2 alone is sufficient to induce 2CLCs with induction of 2C genes and an expanded potency. Mechanistically, miR-344 is activated by the 2C-state driver DUX and post-transcriptionally represses ZMYM2 and LSD1, which recruit the HDAC corepressor to MERVL LTR for transcriptional repression. Consistently, zygotic depletion of Zmym2 compromises the totipotency-to-pluripotency transition during early development. Our studies establish the novel DUX->miR-344--|Zmym2/Lsd1 axis that controls MERVL for expanded stem cell potency.

小鼠胚胎干细胞（Mouse embryonic stem cells, ESCs）会偶发性表达着床前二细胞期（preimplantation two-cell-stage, 2C）转录本，包括MERVL内源性逆转录病毒（MERVL endogenous retrovirus）与Zscan4簇基因（Zscan4 cluster genes）。此类二细胞样细胞（2C-like cells, 2CLCs）若被重新导入早期胚胎，可参与胚胎组织与胚外组织的形成。我们对2CLCs的全局核小体占据谱与基因表达情况进行了分析，并鉴定出miR-344作为正向调控2CLCs潜能的非编码分子。研究发现，仅单独激活内源性MERVL或miR-344-2，即可诱导产生2CLCs，同时激活2C基因并赋予其拓展的发育潜能。机制层面上，miR-344受二细胞状态调控因子DUX激活，并通过转录后途径抑制ZMYM2与LSD1；这两种蛋白可招募HDAC共抑制因子（HDAC corepressor）至MERVL长末端重复序列（MERVL long terminal repeat, LTR）以介导转录抑制。与此一致的是，合子Zmym2敲除会损害早期发育过程中全能性向多能性的转变。本研究确立了全新的DUX→miR-344——|Zmym2/Lsd1调控轴，该轴通过调控MERVL以赋予干细胞拓展的发育潜能。