During early development the vertebrate embryo elongates through a combination of tissue shape change, growth and progenitor cell expansion across multiple regions of the body axis. How these events are coordinated across the length of the embryo to generate a well-proportioned body axis is unknown. Understanding the multi-tissue interplay of morphogenesis, growth and cell fate specification is essential for us to gain a complete understanding how diverse body plans have evolved in a robust manner. Within the posterior region of the embryo, a population of bipotent neuromesodermal progenitors generate both spinal cord and paraxial mesoderm derivatives during the elongation of the vertebrate body. Here we summarize recent data comparing neuromesodermal lineage and their underlying gene-regulatory networks between species and through development. We find that the common characteristic underlying this population is a competence to generate posterior neural and paraxial mesoderm cells, with a conserved Wnt/FGF and Sox2/T/Tbx6 regulatory network. We propose the hypothesis that by maintaining a population of multi-germ layer competent progenitors at the posterior aspect of the embryo, a flexible pool of progenitors is maintained whose contribution to the elongating body axis varies as a consequence of the relative growth rates occurring within anterior and posterior regions of the body axis. We discuss how this capacity for variation in the proportions and rates of NM specification might have been important allowing for alterations in the timing of embryo growth during evolution.

在早期发育过程中，脊椎动物胚胎通过组织形状变化、生长和祖细胞在身体轴多个区域的扩张相结合而伸长。这些事件如何在胚胎的长度上协调以产生匀称的身体轴尚不清楚。了解形态发生、生长和细胞命运规范的多组织相互作用对于我们全面了解不同的身体计划如何以稳健的方式进化至关重要。在胚胎的后部区域，一群双能神经中胚层祖细胞在脊椎动物体伸长过程中产生脊髓和近轴中胚层衍生物。在这里，我们总结了最新的数据，比较了物种之间和发育过程中的神经中胚层谱系及其潜在的基因调控网络。我们发现该群体的共同特征是产生后神经和近轴中胚层细胞的能力，具有保守的 Wnt/FGF 和 Sox2/T/Tbx6 调节网络。我们提出这样的假设：通过在胚胎的后部维持具有多胚层能力的祖细胞群，可以维持一个灵活的祖细胞池，其对延长体轴的贡献因前部内发生的相对生长速率而变化。和身体轴的后部区域。我们讨论了这种 NM 规范的比例和速率变化的能力对于进化过程中胚胎生长时间的改变可能是多么重要。