This article is concerned with the roles of retinoids and other known anterior–posterior morphogens in setting up the embryonic vertebrate anterior–posterior axis. The discussion is restricted to the very earliest events in setting up the anterior–posterior axis (from blastula to tailbud stages in Xenopus embryos). In these earliest developmental stages, morphogen concentration gradients are not relevant for setting up this axis. It emerges that at these stages, the core patterning mechanism is timing: BMP‐anti BMP mediated time space translation that regulates Hox temporal and spatial collinearities and Hox‐Hox auto‐ and cross‐ regulation. The known anterior–posterior morphogens and signaling pathways––retinoids, FGF's, Cdx, Wnts, Gdf11 and others––interact with this core mechanism at and after space–time defined “decision points,” leading to the separation of distinct axial domains. There are also other roles for signaling pathways. Besides the Hox regulated hindbrain/trunk part of the axis, there is a rostral part (including the anterior part of the head and the extreme anterior domain [EAD]) that appears to be regulated by additional mechanisms. Key aspects of anterior–posterior axial patterning, including: the nature of different phases in early patterning and in the whole process; the specificities of Hox action and of intercellular signaling; and the mechanisms of Hox temporal and spatial collinearities, are discussed in relation to the facts and hypotheses proposed above.

中文翻译：

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类视黄醇、其他形态发生素和 Hox 基因在建立脊椎动物体轴方面发挥什么作用？

本文关注类维生素A和其他已知的前后形态发生素在建立胚胎脊椎动物前后轴中的作用。讨论仅限于建立前后轴（从爪蟾胚胎的囊胚到尾芽阶段）的最早事件。在这些最早的发育阶段，形态发生素浓度梯度与建立该轴无关。看来，在这些阶段，核心模式机制是时序：BMP反BMP介导的时空翻译，调节Hox时间和空间共线性以及Hox-Hox自动和交叉调节。已知的前后形态发生素和信号通路——类维生素A、FGF、Cdx、Wnts、Gdf11等——在时空定义的“决策点”处和之后与这一核心机制相互作用，导致不同轴向域的分离。信号通路还有其他作用。除了Hox调节的轴的后脑/躯干部分外，还有一个吻端部分（包括头部的前部和最前部区域 [EAD]）似乎受到其他机制的调节。前后轴模式的关键方面，包括：早期模式和整个过程中不同阶段的性质；Hox作用和细胞间信号传导的特异性；以及Hox时间和空间共线性的机制，根据上面提出的事实和假设进行了讨论。