Olson David J, Oh Denise, Houston Douglas W
The University of Iowa, Department of Biology, 257 BB, Iowa City, IA 52242-1324, USA.
The University of Iowa, Department of Biology, 257 BB, Iowa City, IA 52242-1324, USA.
Dev Biol. 2015 May 15;401(2):249-63. doi: 10.1016/j.ydbio.2015.01.028. Epub 2015 Mar 7.
The self-organization of dorsally-directed microtubules during cortical rotation in the Xenopus egg is essential for dorsal axis formation. The mechanisms controlling this process have been problematic to analyze, owing to difficulties in visualizing microtubules in living egg. Also, the order of events occurring at the onset of cortical rotation have not been satisfactorily visualized in vivo and have been inferred from staged fixed samples. To address these issues, we have characterized the dynamics of total microtubule and plus end behavior continuously throughout cortical rotation, as well as in oocytes and unfertilized eggs. Here, we show that the nascent microtubule network forms in the cortex but associates with the deep cytoplasm at the start of rotation. Importantly, plus ends remain cortical and become increasingly more numerous and active prior to rotation, with dorsal polarization occurring rapidly after the onset of rotation. Additionally, we show that vegetally localized Trim36 is required to attenuate dynamic plus end growth, suggesting that vegetal factors are needed to locally coordinate growth in the cortex.
非洲爪蟾卵皮质旋转过程中背向微管的自组织对于背轴形成至关重要。由于难以在活卵中可视化微管，控制这一过程的机制一直难以分析。此外，皮质旋转开始时发生的事件顺序在体内尚未得到令人满意的可视化，而是从分期固定样本中推断出来的。为了解决这些问题，我们在整个皮质旋转过程中，以及在卵母细胞和未受精卵中，持续表征了总微管和正端行为的动态变化。在此，我们表明新生微管网络在皮质中形成，但在旋转开始时与深层细胞质相关联。重要的是，正端在旋转之前保持在皮质中，并且数量越来越多且活性越来越高，旋转开始后背侧极化迅速发生。此外，我们表明植物定位的Trim36是减弱动态正端生长所必需的，这表明植物因子需要在皮质中局部协调生长。
