Segmentation is a fundamental feature of the vertebrate body plan. This metameric organization is first implemented by somitogenesis in the early embryo, when paired epithelial blocks called somites are rhythmically formed to flank the neural tube. Recent advances in in vitro models have offered new opportunities to elucidate the mechanisms that underlie somitogenesis. Notably, models derived from human pluripotent stem cells introduced an efficient proxy for studying this process during human development. In this Review, we summarize the current understanding of somitogenesis gained from both in vivo studies and in vitro studies. We deconstruct the spatiotemporal dynamics of somitogenesis into four distinct modules: dynamic events in the presomitic mesoderm, segmental determination, somite anteroposterior polarity patterning, and epithelial morphogenesis. We first focus on the segmentation clock, as well as signalling and metabolic gradients along the tissue, before discussing the clock and wavefront and other models that account for segmental determination. We then detail the molecular and cellular mechanisms of anteroposterior polarity patterning and somite epithelialization.

分段是脊椎动物身体计划的基本特征。这种同质异体组织首先是通过早期胚胎中的体节发生实现的，当时称为体节的成对上皮块有节奏地形成在神经管的侧面。体外模型的最新进展为阐明体细胞发生机制提供了新的机会。值得注意的是，源自人类多能干细胞的模型为研究人类发育过程中的这一过程引入了有效的代理。在这篇综述中，我们总结了目前从体内研究和体外研究中获得的对体节发生的理解。我们将体节发生的时空动力学解构为四个不同的模块：体节前中胚层的动态事件、节段决定、体节前后极性模式和上皮形态发生。我们首先关注分段时钟，以及沿组织的信号传导和代谢梯度，然后讨论时钟和波前以及其他解释分段确定的模型。然后，我们详细介绍了前后极性模式和体节上皮化的分子和细胞机制。