Schroeder M M, Gard D L
Department of Biology, Salt Lake City, Utah 84112.
Development. 1992 Mar;114(3):699-709. doi: 10.1242/dev.114.3.699.
Anti-tubulin antibodies and confocal immunofluorescence microscopy were used to examine the organization and regulation of cytoplasmic and cortical microtubules during the first cell cycle of fertilized Xenopus eggs. Appearance of microtubules in the egg cortex temporally coincided with the outgrowth of the sperm aster. Microtubules of the sperm aster first reached the animal cortex at 0.25, (times normalized to first cleavage), forming a radially organized array of cortical microtubules. A disordered network of microtubules was apparent in the vegetal cortex as early as 0.35. Cortical microtubule networks of both animal and vegetal hemispheres were reorganized at times corresponding to the cortical rotation responsible for specification of the dorsal-ventral (D-V) axis. Optical sections suggest that the cortical microtubules are continuous with the microtubules of the sperm aster in fertilized eggs, or an extensive activation aster in activated eggs. Neither assembly and organization, nor disassembly of the cortical microtubules coincided with MPF activation during mitosis. However, cycloheximide or 6-dimethylaminopurine, which arrest fertilized eggs at interphase, blocked cortical microtubule disassembly. Injection of p13, a protein that specifically inhibits MPF activation, delayed or inhibited cortical microtubule breakdown. In contrast, eggs injected with cyc delta 90, a truncated cyclin that arrest eggs in M-phase, showed normal microtubule disassembly. Finally, injection of partially purified MPF into cycloheximide-arrested eggs induced cortical microtubule breakdown. These results suggest that, despite a lack of temporal coincidence, breakdown of the cortical microtubules is dependent on the activation of MPF.
利用抗微管蛋白抗体和共聚焦免疫荧光显微镜技术，研究了非洲爪蟾受精卵第一次细胞周期中细胞质和皮层微管的组织与调控。卵皮层中微管的出现与精子星体的生长在时间上相吻合。精子星体的微管在0.25时（时间归一化至第一次卵裂）首先到达动物皮层，形成径向排列的皮层微管阵列。早在0.35时，植物皮层中就出现了无序的微管网络。动物半球和植物半球的皮层微管网络在与负责背腹（D-V）轴特化的皮层旋转相对应的时间进行了重组。光学切片显示，受精卵中的皮层微管与精子星体的微管连续，或与激活卵中的广泛激活星体连续。在有丝分裂期间，皮层微管的组装、组织和解聚均与MPF激活不同步。然而，能使受精卵停滞在间期的放线菌酮或6-二甲基氨基嘌呤可阻止皮层微管的解聚。注射特异性抑制MPF激活的蛋白p13可延迟或抑制皮层微管的解体。相反，注射能使卵停滞在M期的截短型细胞周期蛋白cyc delta 90的卵，其微管解体正常。最后，向放线菌酮阻滞的卵中注射部分纯化的MPF可诱导皮层微管解体。这些结果表明，尽管时间上不同步，但皮层微管的解体依赖于MPF的激活。
