Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650 Banyuls-sur-Mer, France.
Development. 2022 May 15;149(10). doi: 10.1242/dev.200252. Epub 2022 May 16.
The fibroblast growth factor (FGF) signalling pathway plays various roles during vertebrate embryogenesis, from mesoderm formation to brain patterning. This diversity of functions relies on the fact that vertebrates possess the largest FGF gene complement among metazoans. In the cephalochordate amphioxus, which belongs to the chordate clade together with vertebrates and tunicates, we have previously shown that the main role of FGF during early development is the control of rostral somite formation. Inhibition of this signalling pathway induces the loss of these structures, resulting in an embryo without anterior segmented mesoderm, as in the vertebrate head. Here, by combining several approaches, we show that the anterior presumptive paraxial mesoderm cells acquire an anterior axial fate when FGF signal is inhibited and that they are later incorporated in the anterior notochord. Our analysis of notochord formation in wild type and in embryos in which FGF signalling is inhibited also reveals that amphioxus anterior notochord presents transient prechordal plate features. Altogether, our results give insight into how changes in FGF functions during chordate evolution might have participated to the emergence of the complex vertebrate head.
成纤维细胞生长因子（FGF）信号通路在脊椎动物胚胎发生过程中发挥着各种作用，从中胚层形成到脑模式形成。这种功能的多样性依赖于这样一个事实，即脊椎动物拥有后生动物中最大的 FGF 基因组合。在头索动物文昌鱼中，文昌鱼与脊椎动物和被囊动物一起属于脊索动物分支，我们之前已经表明，FGF 在早期发育中的主要作用是控制头部节段体节的形成。抑制这种信号通路会导致这些结构的丢失，从而导致胚胎没有前部分节中胚层，就像在脊椎动物头部一样。在这里，我们通过结合几种方法表明，当 FGF 信号被抑制时，前假定轴旁中胚层细胞获得了前轴的命运，并且它们后来被纳入前脊索中。我们对野生型和抑制 FGF 信号的胚胎中的脊索形成的分析也表明，文昌鱼的前脊索呈现出短暂的前板特征。总的来说，我们的结果深入了解了在脊椎动物进化过程中 FGF 功能的变化如何参与了复杂的脊椎动物头部的出现。
