Kageura H
Department of Biology, Faculty of Science, Fukuoka University, Japan.
Development. 1997 Apr;124(8):1543-51. doi: 10.1242/dev.124.8.1543.
In eggs of Xenopus laevis, dorsal development is activated on the future dorsal side by cortical rotation, after fertilization. The immediate effect of cortical rotation is probably the transport of a dorsal determinant from the vegetal pole to the equatorial region on the future dorsal side. However, the identity and action of the dorsal determinant remain problematic. In the present experiments, individual isolated cortices from various regions of the unfertilized eggs and embryos were implanted into one of several positions of a recipient 8-cell embryo. The incidence of secondary axes was used not only to locate the cortical dorsal determinant at different times but also to locate the region of the core competent to respond to the dorsal determinant. The dorsal axis-inducing activity of the cortex occurred around the vegetal pole of the unfertilized egg. During cortical rotation, it shifted from there to a wide dorsal region. This is apparently the first evidence for the presence of a dorsal determinant in the egg cortex. The competence of the core of the 8-cell embryo was distributed in the form of gradient with the highest responsiveness at the equator. These results suggest that, in the normal embryo, dorsal development is activated by contact between the cortical dorsal determinant and the equatorial core cytoplasm, brought together through cortical rotation.
在非洲爪蟾的卵中，受精后皮质旋转会在未来的背侧激活背侧发育。皮质旋转的直接作用可能是将一个背侧决定因子从植物极运输到未来背侧的赤道区域。然而，背侧决定因子的身份和作用仍然存在问题。在本实验中，将未受精卵和胚胎不同区域的单个分离皮质植入受体8细胞胚胎的几个位置之一。次级轴的发生率不仅用于在不同时间定位皮质背侧决定因子，还用于定位能够对背侧决定因子作出反应的核心区域。皮质的背侧轴诱导活性发生在未受精卵的植物极周围。在皮质旋转过程中，它从那里转移到一个宽阔的背侧区域。这显然是卵皮质中存在背侧决定因子的首个证据。8细胞胚胎核心的感受态以梯度形式分布，在赤道处反应性最高。这些结果表明，在正常胚胎中，背侧发育是通过皮质背侧决定因子与通过皮质旋转聚集在一起的赤道核心细胞质之间的接触而被激活的。
