Dynamics of two key maternal factors that initiate zygotic regulatory programs in ascidian embryos
Dynamics of two key maternal factors that initiate zygotic regulatory programs in ascidian embryos
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DOI：
10.1016/j.ydbio.2018.03.009
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发表时间：
2018-05-01
影响因子：
2.7
通讯作者：
Satou, Yutaka
中科院分区：
文献类型：
--
作者：
Oda-Ishii, Izumi;Abe, Tetsuya;Satou, Yutaka
在动物胚胎中，转录在受精后的一段时间内受到抑制。在海鞘，玻璃海鞘（A型;或Ciona robusta）的胚胎中，调控基因的转录在8或16细胞阶段之前被抑制。这种最初的转录静止是重要的，使最初的差异基因表达模式的建立沿着动物植物轴的母系因素，因为第三次细胞分裂分离的动物和植物半球成不同的卵裂球。事实上，母体转录因子直接激活合子基因表达的16细胞阶段; Tcf 7/β-连环蛋白激活基因在植物半球，Gata. a激活基因在动物半球。在本研究中，我们揭示了Gata. a和β-连环蛋白的动态，以及它们的靶基因的表达谱。β-连环蛋白在16-细胞期开始移位进入细胞核，因此β-连环蛋白靶的表达在16-细胞期开始。虽然Gata. a在8-细胞阶段之前大量存在，但Gata. a靶标的转录在4-细胞阶段和之前被抑制，并且它们的表达在8-细胞阶段开始。在早期胚胎中，β-连环蛋白靶点的转录可能受到相同机制的抑制，因为在用GSK抑制剂处理的4细胞胚胎中，β-连环蛋白靶点不表达，其中β-连环蛋白易位到细胞核中。因此，这两种母体因素具有不同的动力学，这为16细胞胚胎中的合子遗传程序建立了前模式。
In animal embryos, transcription is repressed for a definite period of time after fertilization. In the embryo of the ascidian, Ciona intestinalis (type A; or Ciona robusta), transcription of regulatory genes is repressed before the 8- or 16-cell stages. This initial transcriptional quiescence is important to enable the establishment of initial differential gene expression patterns along the animal vegetal axis by maternal factors, because the third cell division separates the animal and vegetal hemispheres into distinct blastomeres. Indeed, maternal transcription factors directly activate zygotic gene expression by the 16-cell stage; Tcf7/beta-catenin activates genes in the vegetal hemisphere, and Gata.a activates genes in the animal hemisphere. In the present study, we revealed the dynamics of Gata.a and beta-catenin, and expression profiles of their target genes precisely. beta-catenin began to translocate into the nuclei at the 16-cell stage, and thus expression of P-catenin targets began at the 16-cell stage. Although Gata.a is abundantly present before the 8-cell stage, transcription of Gata.a targets was repressed at and before the 4-cell stage, and their expression began at the 8-cell stage. Transcription of the beta-catenin targets may be repressed by the same mechanism in early embryos, because 13-catenin targets were not expressed in 4-cell embryos treated with a GSK inhibitor, in which P-catenin translocated to the nuclei. Thus, these two maternal factors have different dynamics, which establish the pre-pattern for zygotic genetic programs in 16-cell embryos.