Black S D, Vincent J P
Department of Molecular Biology, University of California, Berkeley 94720.
Dev Biol. 1988 Jul;128(1):65-71. doi: 10.1016/0012-1606(88)90267-9.
In eggs of Xenopus laevis, the meridian of sperm entry (SEP meridian), the direction of subcortical rotation, and the first cleavage furrow have been used to predict, with varying degrees of accuracy, the position of the plane of bilateral symmetry of the embryo. We show here that altering the shape of the uncleaved egg by lateral compression disrupts some of these topographical relationships in a reproducible way. The neural groove, which identifies the embryonic dorsal midline, usually forms at either of the two narrow ends of the compressed egg, regardless of the position of the SEP meridian, whereas the first cleavage furrow divides the compressed egg across its shorter dimension, regardless of the position of the SEP meridian. Thus the positions of the SEP meridian, the cleavage plane, and the embryonic bilateral plane can be completely uncoupled from each other. In contrast, the direction of subcortical rotation is usually parallel to the plane of compression and predicts the position of the neural groove in all cases. Since the direction of subcortical rotation and the plane of bilateral symmetry still correlate under conditions of compression, we conclude that subcortical rotation is the crucial early step in the process of axis specification.
在非洲爪蟾的卵中，精子入卵子午线（SEP子午线）、皮层下旋转方向以及第一次卵裂沟，已被用于不同程度准确地预测胚胎双侧对称平面的位置。我们在此表明，通过侧向挤压改变未受精卵的形状，会以可重复的方式破坏其中一些拓扑关系。识别胚胎背中线的神经沟，通常在压缩卵的两个窄端之一形成，而与SEP子午线的位置无关，而第一次卵裂沟则将压缩卵沿其较短维度分割，同样与SEP子午线的位置无关。因此，SEP子午线、卵裂平面和胚胎双侧平面的位置可以完全相互解耦。相比之下，皮层下旋转方向通常与压缩平面平行，并且在所有情况下都能预测神经沟的位置。由于在压缩条件下皮层下旋转方向与双侧对称平面仍然相关，我们得出结论，皮层下旋转是轴特化过程中关键的早期步骤。
