McEwen B F, Ding Y, Heagle A B
Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, Albany 12201-0509, USA.
Chromosome Res. 1998 Feb;6(2):123-32. doi: 10.1023/a:1009239013215.
Chromosomes attach to the mitotic spindle via their kinetochores. The average number of spindle microtubules binding to each kinetochore varies with species, the stage of mitosis, and the length of time that the kinetochore has been attached to the spindle. In this report, we investigate how kinetochore microtubule number varies with kinetochore size and chromosome size in PtK1 cells. From an analysis of serial-section electron micrographs, we determined that the average surface area of metaphase, taxol-treated metaphase, and anaphase kinetochores is 0.16 +/- 0.05 microm2 (N = 181). Surprisingly, kinetochore microtubules are packed more densely on the smaller kinetochores, as seen by a reduction in the average spacing between kinetochore microtubules from 89 nm to 59 nm. Our interpretation of this result is that PtK1 cells require a minimum kinetochore microtubule-binding capacity for survival during repeated rounds of mitotic division. We estimate the lower limit to be 23 kinetochore microtubules and suggest that this capacity is required to ensure stable attachment during the dynamic and highly stochastic process of kinetochore fiber formation. There is a modest but statistically significant increase in kinetochore microtubule number with chromosome size, indicating that chromosome size is a minor determinant of kinetochore microtubule number.
染色体通过其动粒附着于有丝分裂纺锤体。每个动粒结合的纺锤体微管的平均数量因物种、有丝分裂阶段以及动粒与纺锤体附着的时间长度而异。在本报告中，我们研究了PtK1细胞中动粒微管数量如何随动粒大小和染色体大小而变化。通过对连续切片电子显微镜照片的分析，我们确定中期、紫杉醇处理的中期和后期动粒的平均表面积为0.16±0.05平方微米（N = 181）。令人惊讶的是，动粒微管在较小的动粒上排列得更为密集，从动粒微管之间的平均间距从89纳米减小到59纳米可以看出。我们对这一结果的解释是，PtK1细胞在反复进行有丝分裂的过程中，需要最小的动粒微管结合能力来维持生存。我们估计下限为23根动粒微管，并认为这种能力是确保在动粒纤维形成的动态且高度随机的过程中稳定附着所必需的。动粒微管数量随染色体大小有适度但在统计学上显著的增加，表明染色体大小是动粒微管数量的次要决定因素。
