Alsop G Bradley, Zhang Dahong
Department of Zoology/Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331, USA.
J Cell Sci. 2004 Mar 15;117(Pt 8):1591-602. doi: 10.1242/jcs.01007.
We systematically examined the impact of microtubules on distribution of actin filaments and positioning of cell cleavage using micromanipulation to progressively alter the symmetric distribution of spindle microtubules in grasshopper spermatocytes. The initial microtubule asymmetry was induced by placing a single chromosome at one spindle pole using a microneedle, which facilitates regional assembly of spindle microtubules. We augmented chromosome-induced microtubule asymmetry by further removing the aster from the achromosomal pole, producing unichromosome-bearing monopolar spindles. We created the highest spindle asymmetry by cutting early anaphase cells in two, each containing a full set of segregating chromosomes in a half-spindle. We demonstrate that the location of the spindle midzone, distribution of actin filaments, and position of cell cleavage depend on the amount of microtubule asymmetry generated, shifting up to 48.6+/-3.8% away from the spindle equator in cut cells. The positional shift is dynamic, changing incessantly as spindle microtubules reorganize during cytokinesis. These results suggest that microtubules continuously dictate the distribution of actin filaments and positioning of cell cleavage in grasshopper spermatocytes.
我们通过显微操作逐步改变蝗虫精母细胞纺锤体微管的对称分布，系统地研究了微管对肌动蛋白丝分布和细胞分裂定位的影响。最初的微管不对称是通过用微针将一条染色体置于一个纺锤体极来诱导的，这有利于纺锤体微管的区域组装。我们通过进一步从无染色体极去除星体来增强染色体诱导的微管不对称，从而产生带有单条染色体的单极纺锤体。我们通过将早后期细胞切成两半，每一半都含有一组完整的在半纺锤体中分离的染色体，创造了最高的纺锤体不对称。我们证明，纺锤体中区的位置、肌动蛋白丝的分布和细胞分裂的位置取决于产生的微管不对称量，在切割细胞中可向远离纺锤体赤道的方向移动高达48.6±3.8%。位置变化是动态的，随着细胞分裂过程中纺锤体微管的重新组织而不断变化。这些结果表明，微管持续决定着蝗虫精母细胞中肌动蛋白丝的分布和细胞分裂的定位。
