Transcription factor AP-2γ induces early Cdx2 expression and represses HIPPO signaling to specify the trophectoderm lineage
Transcription factor AP-2γ induces early Cdx2 expression and represses HIPPO signaling to specify the trophectoderm lineage
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DOI：
10.1242/dev.120238
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发表时间：
2015-05-01
期刊：
影响因子：
4.6
通讯作者：
Knott, Jason G.
中科院分区：
文献类型：
--
作者：
Cao, Zubing;Carey, Timothy S.;Knott, Jason G.
细胞命运的决定是多细胞生物发育的基础。在哺乳动物中，第一个细胞命运决定涉及多能内层细胞群和滋养外胚层的分离，这一过程由细胞极性蛋白、HIPPO信号和谱系特异性转录因子（如CDX2）调节。然而，在滋养外胚层谱系的上游调控机制尚未建立。在这里，我们报道了转录因子AP-2 γ (TFAP2C)在小鼠中作为Cdx2表达和位置依赖性HIPPO信号传导的新型上游调节剂。功能缺失和功能获得研究以及启动子分析表明，在发育早期，TFAP2C与内含子增强子的结合是激活Cdx2表达所必需的。在8细胞到桑葚胚的转变过程中，TFAP2C增强细胞极性，抑制卵裂球外部的HIPPO信号。TFAP2C缺失引发了PARD6B的下调、顶端细胞极性的丧失、F-actin的紊乱以及卵裂球外部HIPPO信号的激活。使用Pard6b mRNA的救援实验恢复了细胞极性，但仅部分纠正了位置依赖性的HIPPO信号传导，表明TFAP2C通过多种途径负调控HIPPO信号传导。几个参与肌动蛋白细胞骨架调控的基因（包括Rock1， Rock2）在tfap2c缺失的胚胎中下调。在8细胞向桑葚体转变的过程中，ROCK1和ROCK2活性的抑制导致TFAP2C敲低，引发位置依赖性HIPPO信号的缺失和Cdx2表达的降低。总之，这些结果表明，TFAP2C通过作为Cdx2转录、细胞极性和位置依赖性HIPPO信号传导的关键调节因子，促进了滋养外胚层谱系的确定。
Cell fate decisions are fundamental to the development of multicellular organisms. In mammals the first cell fate decision involves segregation of the pluripotent inner cell mass and the trophectoderm, a process regulated by cell polarity proteins, HIPPO signaling and lineage-specific transcription factors such as CDX2. However, the regulatory mechanisms that operate upstream to specify the trophectoderm lineage have not been established. Here we report that transcription factor AP-2 gamma (TFAP2C) functions as a novel upstream regulator of Cdx2 expression and position-dependent HIPPO signaling in mice. Loss- and gain-of-function studies and promoter analysis revealed that TFAP2C binding to an intronic enhancer is required for activation of Cdx2 expression during early development. During the 8-cell to morula transition TFAP2C potentiates cell polarity to suppress HIPPO signaling in the outside blastomeres. TFAP2C depletion triggered downregulation of PARD6B, loss of apical cell polarity, disorganization of F-actin, and activation of HIPPO signaling in the outside blastomeres. Rescue experiments using Pard6b mRNA restored cell polarity but only partially corrected position-dependent HIPPO signaling, suggesting that TFAP2C negatively regulates HIPPO signaling via multiple pathways. Several genes involved in regulation of the actin cytoskeleton (including Rock1, Rock2) were downregulated in TFAP2C-depleted embryos. Inhibition of ROCK1 and ROCK2 activity during the 8-cell to morula transition phenocopied TFAP2C knockdown, triggering a loss of position-dependent HIPPO signaling and decrease in Cdx2 expression. Altogether, these results demonstrate that TFAP2C facilitates trophectoderm lineage specification by functioning as a key regulator of Cdx2 transcription, cell polarity and position-dependent HIPPO signaling.