Control of ground-state pluripotency by allelic regulation of Nanog
Control of ground-state pluripotency by allelic regulation of Nanog
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DOI：
10.1038/nature10807
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发表时间：
2012-03-22
期刊：
影响因子：
64.8
通讯作者：
Torres-Padilla, Maria-Elena
中科院分区：
文献类型：
--
作者：
Miyanari, Yusuke;Torres-Padilla, Maria-Elena
多能性是在哺乳动物着床前发育过程中通过全基因组重新编程来建立的，导致了幼稚外胚层的形成。重新编程既涉及表观遗传标记的重置，也涉及多能细胞特异性基因的激活，如Nanog和Oct4(也称为Pou5f1)(1-4)。对这些基因的严格调控对重新编程至关重要，但调节它们在体内表达的机制尚未被发现。在这里，我们证明了Nanog-而不是Oct4-在植入前早期胚胎中是单等位基因表达的。然后，在胚泡晚期幼稚的上胚层向基态多能性过渡期间，Nanog经历了向双等位基因表达的渐进转换。在白血病抑制因子(LIF)和血清中生长的胚胎干细胞(ES)主要表达Nanog，并表现出Nanog基因的异步复制，这是单等位基因表达的特征(5)，但当ES细胞在2I条件下培养时，同时激活两个等位基因，这模拟了体外的多能基态。报告ES细胞的活细胞成像证实了Nanog的等位基因表达，并揭示了等位基因转换。Nanog的等位基因表达是通过成纤维细胞生长因子-细胞外信号调节激酶信号通路来调节的，它伴随着近端启动子的染色质变化，但不依赖于DNA甲基化。Nanog杂合子胚泡具有较少的内细胞团衍生物和延迟的原始内胚层形成，这表明Nanog的双等位基因表达在内细胞团及时成熟为完全重新编程的多能上胚中发挥了作用。我们认为，在染色体水平上严格调控Nanog剂量对于获得发育过程中的基态多能性是必要的。我们的数据强调了等位基因表达在体内控制多能性因子剂量方面的意想不到的作用，为重新编程的调节增加了额外的水平。
Pluripotency is established through genome-wide reprogramming during mammalian pre-implantation development, resulting in the formation of the naive epiblast. Reprogramming involves both the resetting of epigenetic marks and the activation of pluripotent-cell-specific genes such as Nanog and Oct4 (also known as Pou5f1)(1-4). The tight regulation of these genes is crucial for reprogramming, but the mechanisms that regulate their expression in vivo have not been uncovered. Here we show that Nanog-but not Oct4-is monoallelically expressed in early pre-implantation embryos. Nanog then undergoes a progressive switch to biallelic expression during the transition towards ground-state pluripotency in the naive epiblast of the late blastocyst. Embryonic stem (ES) cells grown in leukaemia inhibitory factor (LIF) and serum express Nanog mainly monoallelically and show asynchronous replication of the Nanog locus, a feature of monoallelically expressed genes(5), but ES cells activate both alleles when cultured under 2i conditions, which mimic the pluripotent ground state in vitro. Live-cell imaging with reporter ES cells confirmed the allelic expression of Nanog and revealed allelic switching. The allelic expression of Nanog is regulated through the fibroblast growth factor-extracellular signal-regulated kinase signalling pathway, and it is accompanied by chromatin changes at the proximal promoter but occurs independently of DNA methylation. Nanog-heterozygous blastocysts have fewer inner-cell-mass derivatives and delayed primitive endoderm formation, indicating a role for the biallelic expression of Nanog in the timely maturation of the inner cell mass into a fully reprogrammed pluripotent epiblast. We suggest that the tight regulation of Nanog dose at the chromosome level is necessary for the acquisition of ground-state pluripotency during development. Our data highlight an unexpected role for allelic expression in controlling the dose of pluripotency factors in vivo, adding an extra level to the regulation of reprogramming.