The Grb2/Mek pathway represses Nanog in murine embryonic stem cells
The Grb2/Mek pathway represses Nanog in murine embryonic stem cells
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DOI：
10.1128/mcb.00508-06
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发表时间：
2006-10-01
影响因子：
5.3
通讯作者：
Terada, Naohiro
中科院分区：
文献类型：
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作者：
Hamazaki, Takashi;Kehoe, Sarah M.;Terada, Naohiro
同源盒基因Nanog是胚胎干细胞自我更新的关键内在决定因素，其抑制导致胚胎干细胞选择性分化为原始内胚层。虽然Nanog抑制发生在ES细胞聚集的最外层，独立于白血病抑制因子(LIF)/STAT3途径，但很大程度上不确定是什么外部线索和细胞内信号导致了这一事件。有趣的是，添加酪氨酸磷酸酶抑制剂钒酸钠选择性地抑制了Nanog转录，而上游转录调节因子Oct3/4和Sox2没有任何可检测到的变化。此外，钒酸钠诱导原始内胚层分化，甚至在胚胎干细胞聚集体的内细胞中也是如此。添加钒酸钠后，两种可能的下游Nanog效应物Gata6和Zfp42的表达也分别升高和降低，但这些变化被外源Nanog表达消除。缺乏Grb2或添加Mek抑制剂PD98059可消除钒酸钠的作用。事实上，PD98059也能阻止ES细胞聚集诱导的Nanog抑制。此外，将组成型活性Mek突变体转染到胚胎干细胞中可诱导Nanog抑制和原始内胚层分化。这些数据表明，Grb2/Mek途径主要介导Nanog基因抑制胚胎干细胞向原始内胚层分化。
The homeobox gene Nanog is a key intrinsic determinant of self renewal in embryonic stem (ES) cells, and its repression leads ES cells to selectively differentiate into primitive endoderm. Although Nanog repression occurs at the outermost layer of ES cell aggregates independent of the leukemia inhibitory factor (LIF)/STAT3 pathway, it is largely undetermined what external cues and intracellular signals cause the event. Of interest, addition of the tyrosine phosphatase inhibitor, sodium vanadate, selectively repressed Nanog transcription without any detectable changes in upstream transcriptional regulators Oct3/4 and Sox2. Furthermore, sodium vanadate induced primitive endoderm differentiation, even in the inner cells of ES cell aggregates. Expression of Gata6 and Zfp42, two putative downstream Nanog effectors, was also increased and decreased by the addition of sodium vanadate, respectively, but these changes were eliminated by exogenous Nanog expression. The effects of sodium vanadate were abrogated by Grb2 deficiency or by the addition of the Mek inhibitor, PD98059. Indeed, PD98059 prevented Nanog repression induced by ES cell aggregation as well. Furthermore, transfection of a constitutive active Mek mutant into ES cells induced Nanog repression and primitive endoderm differentiation. These data indicate that the Grb2/Mek pathway primarily mediates Nanog gene repression upon ES cell differentiation into primitive endoderm.