Planar and vertical signals in the induction and patterning of the Xenopus nervous system
Planar and vertical signals in the induction and patterning of the Xenopus nervous system
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作者：
A. R. I. Altaba
我们在完全外原肠胚胚胎（其中轴中胚层似乎与预定的神经外胚层保持分离）以及外胚层和中胚层的重组体中研究了负责非洲爪蟾神经系统形成的细胞机制。显示前后模式的后部神经组织在外原肠胚外胚层中发育。这种效应可能是由在没有下层中胚层的情况下出现的平面信号介导的。后部神经管的形成可能依赖于顶板，这是一个沿着前后轴延伸的中线外胚层细胞群。前脑特征性神经结构以及通常在后神经管腹侧区域发现的细胞类型的诱导需要来自下层轴中胚层的额外垂直信号。因此，非洲爪蟾胚胎神经系统的形成似乎涉及源自中线细胞群的不同平面信号和垂直信号的协同作用。
The cellular mechanisms responsible for the formation of the Xenopus nervous system have been examined in total exogastrula embryos in which the axial mesoderm appears to remain segregated from prospective neural ectoderm and in recombinates of ectoderm and mesoderm. Posterior neural tissue displaying anteroposterior pattern develops in exogastrula ectoderm. This effect may be mediated by planar signals that occur in the absence of underlying mesoderm. The formation of a posterior neural tube may depend on the notoplate, a midline ectodermal cell group which extends along the anteroposterior axis. The induction of neural structures characteristic of the forebrain and of cell types normally found in the ventral region of the posterior neural tube requires additional vertical signals from underlying axial mesoderm. Thus, the formation of the embryonic Xenopus nervous system appears to involve the cooperation of distinct planar and vertical signals derived from midline cell groups.