Sweetman Dylan, Wagstaff Laura, Cooper Oliver, Weijer Cornelis, Münsterberg Andrea
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
BMC Dev Biol. 2008 Jun 9;8:63. doi: 10.1186/1471-213X-8-63.
Co-ordinated cell movement is a fundamental feature of developing embryos. Massive cell movements occur during vertebrate gastrulation and during the subsequent extension of the embryonic body axis. These are controlled by cell-cell signalling and a number of pathways have been implicated. Here we use long-term video microscopy in chicken embryos to visualize the migration routes and movement behaviour of mesoderm progenitor cells as they emerge from the primitive streak (PS) between HH stages 7 and 10.
We observed distinct cell movement behaviours along the length of the streak and determined that this is position dependent with cells responding to environmental cues. The behaviour of cells was altered by exposing embryos or primitive streak explants to cell pellets expressing Wnt3a and Wnt5a, without affecting cell fates, thus implicating these ligands in the regulation of cell movement behaviour. Interestingly younger embryos were not responsive, suggesting that Wnt3a and Wnt5a are specifically involved in the generation of posterior mesoderm, consistent with existing mouse and zebrafish mutants. To investigate which downstream components are involved mutant forms of dishevelled (dsh) and prickle1 (pk1) were electroporated into the primitive streak. These had differential effects on the behaviour of mesoderm progenitors emerging from anterior or posterior regions of the streak, suggesting that multiple Wnt pathways are involved in controlling cell migration during extension of the body axis in amniote embryos.
We suggest that the distinct behaviours of paraxial and lateral mesoderm precursors are regulated by the opposing actions of Wnt5a and Wnt3a as they leave the primitive streak in neurula stage embryos. Our data suggests that Wnt5a acts via prickle to cause migration of cells from the posterior streak. In the anterior streak, this is antagonised by Wnt3a to generate non-migratory medial mesoderm.
协调的细胞运动是发育中胚胎的一个基本特征。在脊椎动物原肠胚形成期间以及随后胚胎体轴的延伸过程中会发生大规模的细胞运动。这些运动受细胞间信号传导控制，并且涉及许多信号通路。在这里，我们使用鸡胚的长期视频显微镜来观察中胚层祖细胞在HH7至10期从原条（PS）出现时的迁移路线和运动行为。
我们观察到沿原条长度存在不同的细胞运动行为，并确定这与位置有关，细胞对环境线索有反应。通过将胚胎或原条外植体暴露于表达Wnt3a和Wnt5a的细胞团中，细胞行为发生改变，而不影响细胞命运，因此表明这些配体参与细胞运动行为的调节。有趣的是，较年轻的胚胎没有反应，这表明Wnt3a和Wnt5a特别参与后中胚层的产生，这与现有的小鼠和斑马鱼突变体一致。为了研究涉及哪些下游成分，将散乱蛋白（dsh）和刺状蛋白1（pk1）的突变形式电穿孔到原条中。这些对从中胚层前区或后区出现的中胚层祖细胞的行为有不同影响，表明多个Wnt信号通路参与羊膜动物胚胎体轴延伸过程中细胞迁移的控制。
我们认为，在神经胚期胚胎中，当近轴和外侧中胚层前体细胞离开原条时，它们的不同行为受Wnt5a和Wnt3a的相反作用调节。我们的数据表明，Wnt5a通过刺状蛋白作用导致细胞从后原条迁移。在前原条中，Wnt3a对此起拮抗作用，以产生不迁移的内侧中胚层。
