Around the time of gastrulation in higher vertebrate embryos, inductive interactions direct cells to form central nervous system (neural plate) or sensory placodes. Grafts of different tissues into the periphery of a chicken embryo elicit different responses: Hensen’s node induces a neural plate whereas the head mesoderm induces placodes. How different are these processes? Transcriptome analysis in time course reveals that both processes start by induction of a common set of genes, which later diverge. These genes are remarkably similar to those induced by an extraembryonic tissue, the hypoblast, and are normally expressed in the pregastrulation stage epiblast. Explants of this epiblast grown in the absence of further signals develop as neural plate border derivatives and eventually express lens markers. We designate this state as “preborder”; its transcriptome resembles embryonic stem cells. Finally, using sequential transplantation experiments, we show that the node, head mesoderm, and hypoblast are interchangeable to begin any of these inductions while the final outcome depends on the tissue emitting the later signals.

中文翻译：

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节点的神经诱导和头部中胚层的基板诱导共享一个类似于神经板边界和 ES 细胞的初始状态

在高等脊椎动物胚胎的原肠胚形成期间，诱导相互作用引导细胞形成中枢神经系统（神经板）或感觉基板。将不同组织移植到鸡胚周围会引起不同的反应：Hensen 结诱导神经板，而头部中胚层诱导基板。这些过程有何不同？时间过程中的转录组分析表明，这两个过程都是从诱导一组共同的基因开始的，后来这些基因发生了分歧。这些基因与由胚外组织、下胚层诱导的基因非常相似，并且通常在前原肠胚期外胚层中表达。在没有进一步信号的情况下生长的这种外胚层的外植体发育为神经板边界衍生物并最终表达晶状体标记。我们将此状态指定为“前边界”；它的转录组类似于胚胎干细胞。最后，使用顺序移植实验，我们表明节点、头部中胚层和下胚层可以互换以开始任何这些诱导，而最终结果取决于发出后期信号的组织。