It is critical to specify a signal that directly drives the transition that occurs between cell states. However, such inferences are often confounded by indirect intercellular communications or secondary transcriptomic changes due to primary transcription factors. Although FGF is known for its importance during mesoderm-to-endothelium differentiation, its specific role and signaling mechanisms are still unclear due to the confounding factors referenced above. Here, we attempted to minimize the secondary artifacts by manipulating FGF and its downstream mediators with a short incubation time before sampling and protein-synthesis blockage in a low-density angioblastic/endothelial differentiation system. In less than 8 h, FGF started the conversion of KDR^low/PDGFRA^low nascent mesoderm into KDR^high/PDGFRA^low angioblasts, and the priming by FGF was necessary to endow endothelial formation 72 h later. Further, the angioblastic conversion was mediated by the FGFR1/BRAF/MEK/ERK pathway in mesodermal cells. Finally, two transcription factors, ETV2 and LMO2, were the early direct functional responders downstream of the FGF pathway, and ETV2 alone was enough to complement the absence of FGF. FGF’s selective role in mediating the first-step, angioblastic conversion from mesoderm-to-endothelium thus allows for refined control over acquiring and manipulating angioblasts. The noise-minimized differentiation/analysis platform presented here is well-suited for studies on the signaling switches of other mesodermal-lineage fates as well.

指定直接驱动发生在单元状态之间的转换的信号至关重要。但是，此类推论通常与间接细胞间通讯或由于初级转录因子引起的二级转录组变化混淆。尽管FGF在中胚层至内皮分化过程中的重要性而闻名，但由于上述混杂因素，其具体作用和信号传导机制仍不清楚。在这里，我们尝试通过在低密度血管母细胞/内皮细胞分化系统中采样和蛋白质合成封闭之前，在较短的孵育时间内操纵FGF及其下游介体，从而将次要伪影最小化。不到8小时，FGF就开始了KDR^低/ PDGFRA^低的转化新生的中胚层进入^高KDR / PDGFRA^低的成血管细胞，而FGF引发必须在72小时后赋予内皮形成。此外，成血管细胞转化是由中胚层细胞中的FGFR1 / BRAF / MEK / ERK途径介导的。最后，两个转录因子ETV2和LMO2是FGF通路下游的早期直接功能应答者，仅ETV2足以弥补FGF的缺乏。FGF在介导中胚层到内皮的第一步成血管细胞转化中的选择性作用因此可以对获取和操纵成血管细胞进行精细控制。这里介绍的噪声最小化的分化/分析平台也非常适合研究其他中胚层谱系命运的信号转导。