ETS transcription factors play an important role in the specification and differentiation of endothelial cells during vascular development. Despite previous studies, the role of the founding member of the ETS family, Ets1, in vascular development in vivo is only partially understood. Here, we generated a zebrafish ets1 mutant by TALEN genome editing and tested functional redundancy between Ets1 and a related ETS factor Etv2/Etsrp/ER71. While zebrafish ets1^−/− mutants have a normal functional vascular system, etv2^−/−;ets1^-/embryos had more severe angiogenic defects and lower expression levels of kdr and kdrl, the two zebrafish homologs of the mammalian Vascular Endothelial Growth Factor Receptor 2 VEGFR2/Flk1, than etv2^−/−embryos. Expression of constitutively active Mitogen-Activated Protein Kinase1 (MAP2K1) within endothelial cells partially rescued this angiogenic defect. Interestingly, ets1^−/− embryos displayed extensive apoptosis within the trunk vasculature despite exhibiting normal vascular patterning. Loss of Ets1 combined with a partial knockdown of Etv2 function resulted in a decrease in endothelial cell numbers in the axial vasculature, which argues for a role of Ets1 in promoting vasculogenesis. We also demonstrate that although both Ets1 and Etv2 can induce ectopic vascular marker expression in zebrafish embryos, Ets1 activity is dependent on MAPK-mediated phosphorylation of its Thr30 and Ser33 residues, while Etv2 activity is not. Together, our results identify a novel function of Ets1 in regulating endothelial cell survival during vasculogenesis in vivo. Based on these findings, we propose a revised model of how Ets1 and Etv2 play unique and partially redundant roles to promote vascular development.

ETS 转录因子在血管发育过程中内皮细胞的规范和分化中起重要作用。尽管有先前的研究，但仅部分了解ETS 家族的创始成员 Ets1在体内血管发育中的作用。在这里，我们通过 TALEN 基因组编辑生成了斑马鱼ets1突变体，并测试了 Ets1 和相关 ETS 因子 Etv2/Etsrp/ER71 之间的功能冗余。虽然斑马鱼ets1 ^-/-突变体具有正常的功能血管系统，但etv2 ^-/- ;ets1 ^-/胚胎具有更严重的血管生成缺陷和较低的kdr和kdrl表达水平，哺乳动物血管内皮生长因子受体 2 VEGFR2/Flk1的两个斑马鱼同系物，而不是etv2 ^-/-胚胎。内皮细胞内组成型活性丝裂原活化蛋白激酶1 ( MAP2K1 ) 的表达部分挽救了这种血管生成缺陷。有趣的是，ets1 ^-/-尽管表现出正常的血管模式，但胚胎在躯干血管内显示出广泛的细胞凋亡。Ets1 的缺失与 Etv2 功能的部分敲低相结合导致轴向脉管系统中的内皮细胞数量减少，这证明 Ets1 在促进血管发生中的作用。我们还证明，虽然 Ets1 和 Etv2 都可以诱导斑马鱼胚胎中的异位血管标志物表达，但 Ets1 的活性依赖于 MAPK 介导的 Thr30 和 Ser33 残基磷酸化，而 Etv2 活性则不是。总之，我们的结果确定了 Ets1在体内血管生成过程中调节内皮细胞存活的新功能。 基于这些发现，我们提出了 Ets1 和 Etv2 如何发挥独特且部分冗余的作用以促进血管发育的修订模型。