Ruiz i Altaba A
Howard Hughes Medical Institute, Columbia University, New York, NY 10032.
Development. 1992 Sep;116(1):67-80. doi: 10.1242/dev.116.1.67.
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.
非洲爪蟾神经系统形成的细胞机制已在全外胚层胚胎以及外胚层与中胚层的重组体中进行了研究。在全外胚层胚胎中，轴向中胚层似乎与预期的神经外胚层保持分离。外胚层中会发育出呈现前后模式的后部神经组织。这种效应可能由在没有下层中胚层的情况下出现的平面信号介导。后神经管的形成可能依赖于脊板，这是一个沿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后神经管腹侧区域通常发现的细胞类型的诱导需要来自下层轴向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来自中线细胞群的不同平面信号和垂直信号的协同作用。
