Kim Sewoon, Kim Hanjun, Tan Anderson, Song Yonghee, Lee Hyeju, Ying Qi-Long, Jho Eek-Hoon
Department of Life Science, University of Seoul, Seoul, Korea.
Asan Institute for Life Sciences, Seoul, Korea.
Int J Stem Cells. 2020 Jul 30;13(2):192-201. doi: 10.15283/ijsc20044.
Tcfs and Lef1 are DNA-binding transcriptional factors in the canonical Wnt signaling pathway. In the absence of -catenin, Tcfs and Lef1 generally act as transcriptional repressors with co-repressor proteins such as Groucho, CtBP, and HIC-5. However, Tcfs and Lef1 turn into transcriptional activators during the interaction with -catenin. Therefore, the activity of Tcfs and Lef1 is regulated by -catenin. However, the intrinsic role of Tcfs and Lef1 has yet to be examined. The purpose of this study was to determine whether Tcfs and Lef1 play differential roles in the regulation of self-renewal and differentiation of mouse ES cells.
Interestingly, the expression of Tcfs and Lef1 was dynamically altered under various differentiation conditions, such as removal of LIF, EB formation and neuronal differentiation in N2B27 media, suggesting that the function of each Tcf and Lef1 may vary in ES cells. Ectopic expression of Tcf1 or the dominant negative form of Lef1 (Lef1-DN) contributes to ES cells to self-renew in the absence of leukemia inhibitory factor (LIF), whereas ectopic expression of Tcf3, Lef1 or Tcf1-DN did not support ES cells to self-renew. Ectopic expression of either Lef1 or Lef1-DN blocked neuronal differentiation, suggesting that the transient induction of Lef1 was necessary for the initiation and progress of differentiation. ChIP analysis shows that Tcf1 bound to Nanog promoter and ectopic expression of Tcf1 enhanced the transcription of Nanog.
The overall data suggest that Tcf1 plays a critical role in the maintenance of stemness whereas Lef1 is involved in the initiation of differentiation.
Tcf和Lef1是经典Wnt信号通路中的DNA结合转录因子。在没有β-连环蛋白的情况下，Tcf和Lef1通常与共抑制蛋白（如Groucho、CtBP和HIC-5）一起作为转录抑制因子发挥作用。然而，Tcf和Lef1在与β-连环蛋白相互作用时会转变为转录激活因子。因此，Tcf和Lef1的活性受β-连环蛋白调节。然而，Tcf和Lef1的内在作用尚未得到研究。本研究的目的是确定Tcf和Lef1在小鼠胚胎干细胞自我更新和分化的调节中是否发挥不同作用。
有趣的是，在各种分化条件下，如去除白血病抑制因子（LIF）、形成胚体以及在N2B27培养基中进行神经元分化时，Tcf和Lef1的表达会动态变化，这表明每个Tcf和Lef1在胚胎干细胞中的功能可能不同。Tcf1的异位表达或Lef1的显性负性形式（Lef1-DN）有助于胚胎干细胞在没有白血病抑制因子（LIF）的情况下自我更新，而Tcf3、Lef1或Tcf1-DN的异位表达则不支持胚胎干细胞自我更新。Lef1或Lef1-DN的异位表达均阻断了神经元分化，这表明Lef1的短暂诱导对于分化的起始和进展是必要的。染色质免疫沉淀分析表明，Tcf1与Nanog启动子结合，Tcf1的异位表达增强了Nanog的转录。
总体数据表明，Tcf1在维持干性方面起关键作用，而Lef1参与分化的起始。
