Kinematics of gray crescent formation in Xenopus eggs: the displacement of subcortical cytoplasm relative to the egg surface.
Kinematics of gray crescent formation in Xenopus eggs: the displacement of subcortical cytoplasm relative to the egg surface.
复制标题
非洲爪蟾卵中灰色新月形形成的运动学：皮层下细胞质相对于卵表面的位移。
DOI：
10.1016/0012-1606(86)90184-3
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发表时间：
1986
影响因子：
2.7
通讯作者：
Gerhart,JC
中科院分区：
文献类型：
--
作者：
Vincent,JP;Oster,GF;Gerhart,JC
两栖动物背腹轴的特化发生在受精和第一次卵裂之间的灰色新月形形成的时期。在灰色新月形形成的过程中，卵通过一种运动重新组织其外围，对此已有两种描述。根据蛙卵的“旋转假说”，整个卵皮质相对于静止的皮质下细胞质旋转30°，留下新月形区域作为改变颜色的区域。另一方面，为Xenopus和Ranaeggs提出的“收缩假说”声称，在精子进入点有一个皮质收缩，导致相对的赤道带伸展，新月出现。我们通过将一种荧光染料图案（尼罗蓝）印在皮层下细胞质上，将另一种荧光染料图案（荧光素-凝集素）印在卵表面，重新研究了Xenopuseggs的情况。当卵表面通过将卵包埋在明胶中而保持固定时，可以观察到皮质下细胞质的两个主要运动。首先，从时间0.3开始（受精和第一次卵裂之间的时间的30%），动物半球皮层下细胞质向一个点收敛，而植物半球是静止的。这种收敛继续降低强度，直到约0.8的第一个细胞周期。第二，在0.45时，动物和植物皮层下细胞质开始整体旋转，叠加在动物半球会聚上。到0.8-0.9时，旋转完成，皮质下细胞质相对于表面位移30°。这种旋转可靠地将胚胎的未来背中线定位在子午线上，在该子午线上皮层下细胞质的位移在植物方向上最大。在正常的未嵌入的卵子中，当卵子表面自由移动时，它相对于皮质下细胞质旋转30°，皮质下细胞质在重力平衡的位置保持静止。虽然收敛和旋转发生在theXenopusegg，我们给出的证据表明，旋转，而不是收敛（也许等同于收缩），指定胚胎的预期轴。尽管Xenopusegg并不形成典型的灰色新月形，但由于其特殊的色素分布，指定未来胚胎轴的重组过程类似于Ranaegg。
Specification of the amphibian dorso-ventral axis takes place in the period between fertilization and first cleavage when the gray crescent forms. In the course of gray crescent formation, the egg reorganizes its periphery by a movement for which two descriptions have been given. According to the “rotation hypothesis,” which was originated and supported forRanaeggs, the entire egg cortex rotates by an arc of 30° relative to the stationary subcortical cytoplasm, leaving the crescent as a zone of altered coloration. The “contraction hypothesis” on the other hand, which was proposed forXenopusandRanaeggs, asserts that there is a cortical contraction focused at the sperm entry point that leads to stretching of the opposite equatorial zone at which the crescent appears. We have reinvestigated the case ofXenopuseggs by imprinting one kind of fluorescent dye pattern (Nile blue) onto the subcortical cytoplasm and another kind (fluorescein-lectin) onto the egg surface. When the egg surface is held fixed by embedding the egg in gelatin, two major movements of the subcortical cytoplasm are observable. First, starting at time 0.3 (30% of the time between fertilization and first cleavage), the animal hemisphere subcortical cytoplasm converges toward a point, while the vegetal hemisphere is quiescent. This convergence continues with decreasing strength until approximately 0.8 of the first cell cycle. Second, at 0.45, an overall rotation of the animal and vegetal subcortical cytoplasm commences, superimposed on the animal hemisphere convergence. By 0.8–0.9 the rotation is complete, having accomplished a 30° displacement of the subcortical cytoplasm relative to the surface. This rotation reliably locates the future dorsal midline of the embryo at the meridian on which the displacement of the subcortical cytoplasm is greatest in a vegetal direction. In normal unembedded eggs, when the egg surface is free to move, it rotates 30° relative to the subcortical cytoplasm, which remains stationary in a position of gravitational equilibrium. Although both a convergence and rotation occur in theXenopusegg, we give evidence that the rotation, not the convergence (perhaps equated with contraction), specifies the embryo's prospective axis. Even though theXenopusegg does not form a classical gray crescent, due to its particular pigment distribution, the reorganization process which specifies the future embryonic axis resembles that of theRanaegg.