Nayak Pinaki, Chatterjee Saptarshi, Paul Raja
School of Mathematical and Computational Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, USA.
Phys Rev E. 2023 Sep;108(3-1):034401. doi: 10.1103/PhysRevE.108.034401.
Variation in the chromosome numbers can arise from the erroneous mitosis or fusion and fission of chromosomes. While the mitotic errors lead to an increase or decrease in the overall chromosomal substance in the daughter cells, fission and fusion keep this conserved. Variations in chromosome numbers are assumed to be a crucial driver of speciation. For example, the members of the muntjac species are known to have very different karyotypes with the chromosome numbers varying from 2n=70+3B in the brown brocket deer to 2n=46 in the Chinese muntjac and 2n=6/7 in the Indian muntjac. The chromosomal content in the nucleus of these closely related mammals is roughly the same and various chromosome fusion and fission pathways have been suggested as the evolution process of these karyotypes. Similar trends can also be found in lepidoptera and yeast species which show a wide variation of chromosome numbers. The effect of chromosome number variation on the spindle assembly time and accuracy is still not properly addressed. We computationally investigate the effect of conservation of the total chromosomal substance on the spindle assembly during prometaphase. Our results suggest that chromosomal fusion pathways aid the microtubule-driven search and capture of the kinetochore in cells with monocentric chromosomes. We further report a comparative analysis of the site and percentage of amphitelic captures, dependence on cell shape, and position of the kinetochore in respect to chromosomal volume partitioning.
染色体数目的变化可能源于有丝分裂错误或染色体的融合与分裂。有丝分裂错误会导致子细胞中染色体物质总量增加或减少，而融合和分裂则使染色体物质总量保持不变。染色体数目的变化被认为是物种形成的关键驱动因素。例如，麂属物种的成员具有非常不同的核型，染色体数目从褐麂的2n = 70 + 3B到中国麂的2n = 46以及印度麂的2n = 6/7不等。这些亲缘关系密切的哺乳动物细胞核中的染色体含量大致相同，并且已经提出了各种染色体融合和分裂途径作为这些核型的进化过程。在染色体数目变化很大的鳞翅目和酵母物种中也能发现类似趋势。染色体数目变化对纺锤体组装时间和准确性的影响仍未得到妥善解决。我们通过计算研究了前中期染色体物质总量守恒对纺锤体组装的影响。我们的结果表明，染色体融合途径有助于单着丝粒染色体细胞中微管驱动的动粒搜索和捕获。我们还进一步报告了双着丝粒捕获的位点和百分比、对细胞形状的依赖性以及动粒相对于染色体体积分配的位置的比较分析。
