Saint-Jeannet J P, Thiery J P, Koteliansky V E
Laboratoire de Physiopathologie du Développement, CNRS URA 1337, Paris, France.
Dev Biol. 1994 Aug;164(2):374-82. doi: 10.1006/dbio.1994.1207.
Epithelial-mesenchymal interactions are of major importance during development to direct correct differentiation and morphogenesis of embryonic tissues. One subset of lateral mesoderm-derived mesenchymal cells will form the smooth muscle (SM) layer of the primary epithelial lining of hollow internal organs. It has been previously reported that the differentiation of SM cells in Xenopus laevis can be followed by the expression of alpha-SM actin. It was also shown that basic fibroblast growth factor (bFGF) had the ability to induce this actin isoform in isolated blastula animal caps. In this paper, by injection at the two-cell stage of mRNA encoding a truncated form of the FGF receptor which can act as a dominant negative inhibitor, we have analyzed the role of the FGF signaling pathway in the formation of the SM lineage. We have observed that mutated embryos presented significant delay in the differentiation of the SM cells compared to control embryos, demonstrating the importance of this signaling pathway for the formation of the lateral mesoderm-derived SM cells. Moreover, a correlation could be established between this delay and the dramatic defects observed in the morphogenesis of the intestine with which mesenchyme-derived SM cells are normally associated. This phenotype was efficiently rescued by coinjection of the wild-type FGF receptor. Our data suggest that the differentiation of SM cells at the correct time could be an essential event for the proper morphogenesis of the endoderm-derived digestive tract.
上皮-间充质相互作用在胚胎组织的正确分化和形态发生过程中起着至关重要的作用。外侧中胚层来源的间充质细胞的一个亚群将形成中空内脏器官初级上皮衬里的平滑肌（SM）层。先前已有报道，非洲爪蟾中SM细胞的分化可通过α-SM肌动蛋白的表达来追踪。研究还表明，碱性成纤维细胞生长因子（bFGF）能够在分离的囊胚动物帽中诱导这种肌动蛋白异构体的表达。在本文中，通过在两细胞阶段注射编码一种可作为显性负性抑制剂的截短形式FGF受体的mRNA，我们分析了FGF信号通路在SM谱系形成中的作用。我们观察到，与对照胚胎相比，突变胚胎的SM细胞分化出现明显延迟，这表明该信号通路对于外侧中胚层来源的SM细胞的形成至关重要。此外，这种延迟与在通常与间充质来源的SM细胞相关的肠道形态发生中观察到的严重缺陷之间存在相关性。通过共注射野生型FGF受体，这种表型得到了有效挽救。我们的数据表明，SM细胞在正确时间的分化可能是内胚层来源的消化道正常形态发生的一个关键事件。
