Sinkkonen Lasse, Hugenschmidt Tabea, Berninger Philipp, Gaidatzis Dimos, Mohn Fabio, Artus-Revel Caroline G, Zavolan Mihaela, Svoboda Petr, Filipowicz Witold
Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland.
Nat Struct Mol Biol. 2008 Mar;15(3):259-67. doi: 10.1038/nsmb.1391. Epub 2008 Mar 2.
Loss of microRNA (miRNA) pathway components negatively affects differentiation of embryonic stem (ES) cells, but the underlying molecular mechanisms remain poorly defined. Here we characterize changes in mouse ES cells lacking Dicer (Dicer1). Transcriptome analysis of Dicer-/- cells indicates that the ES-specific miR-290 cluster has an important regulatory function in undifferentiated ES cells. Consistently, many of the defects in Dicer-deficient cells can be reversed by transfection with miR-290 family miRNAs. We demonstrate that Oct4 (also known as Pou5f1) silencing in differentiating Dicer-/- ES cells is accompanied by accumulation of repressive histone marks but not by DNA methylation, which prevents the stable repression of Oct4. The methylation defect correlates with downregulation of de novo DNA methyltransferases (Dnmts). The downregulation is mediated by Rbl2 and possibly other transcriptional repressors, potential direct targets of miR-290 cluster miRNAs. The defective DNA methylation can be rescued by ectopic expression of de novo Dnmts or by transfection of the miR-290 cluster miRNAs, indicating that de novo DNA methylation in ES cells is controlled by miRNAs.
微小RNA（miRNA）通路成分的缺失会对胚胎干细胞（ES细胞）的分化产生负面影响，但其潜在的分子机制仍不清楚。在此，我们对缺乏Dicer（Dicer1）的小鼠ES细胞中的变化进行了表征。对Dicer基因敲除细胞的转录组分析表明，ES细胞特异性的miR-290簇在未分化的ES细胞中具有重要的调节功能。一致地，通过转染miR-290家族miRNA可以逆转Dicer缺陷细胞中的许多缺陷。我们证明，在分化的Dicer基因敲除ES细胞中，Oct4（也称为Pou5f1）的沉默伴随着抑制性组蛋白标记的积累，但没有DNA甲基化，这阻止了Oct4的稳定抑制。甲基化缺陷与从头DNA甲基转移酶（Dnmts）的下调相关。这种下调是由Rbl2以及可能的其他转录抑制因子介导的，它们是miR-290簇miRNA的潜在直接靶点。通过异位表达从头Dnmts或转染miR-290簇miRNA可以挽救有缺陷的DNA甲基化，这表明ES细胞中的从头DNA甲基化受miRNA控制。
