Gastrulation consists in the dramatic reorganisation of the epiblast, a one-cell thick epithelial sheet, into a multilayered embryo. In chick, the formation of the internal layers requires the generation of a macroscopic convection-like flow, which involves up to 50,000 epithelial cells in the epiblast. These cell movements locate the mesendoderm precursors into the midline of the epiblast to form the primitive streak. There they acquire a mesenchymal phenotype, ingress into the embryo and migrate outward to populate the inner embryonic layers. This review covers what is currently understood about how cell behaviours ultimately cause these morphogenetic events and how they are regulated. We discuss 1) how the biochemical patterning of the embryo before gastrulation creates compartments of differential cell behaviours, 2) how the global epithelial flows arise from the coordinated actions of individual cells, 3) how the cells delaminate individually from the epiblast during the ingression, and 4) how cells move after the ingression following stereotypical migration routes. We conclude by exploring new technical advances that will facilitate future research in the chick model system.

中文翻译：

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驱动鸟类胚胎原肠胚形成的细胞过程

原肠胚形成包括将单细胞厚的上皮层的外胚层戏剧性地重组为多层胚胎。在雏鸡中，内层的形成需要产生宏观对流样流动，这涉及外胚层中多达 50,000 个上皮细胞。这些细胞运动将中内胚层前体定位到外胚层的中线以形成原始条纹。在那里，它们获得间充质表型，进入胚胎并向外迁移以填充内部胚胎层。这篇综述涵盖了目前对细胞行为如何最终导致这些形态发生事件以及它们如何被调节的理解。我们讨论 1) 原肠胚形成前胚胎的生化模式如何产生不同细胞行为的隔室，2) 全球上皮细胞流动是如何由单个细胞的协调作用产生的，3) 细胞在侵入过程中如何从外胚层单独分层，以及 4) 细胞在侵入后如何按照典型的迁移路线移动。最后，我们探索了新的技术进步，这些进步将促进雏鸡模型系统的未来研究。