Chromosome compaction is a key feature of mitosis and critical for accurate chromosome segregation. However, a precise quantitative analysis of chromosome geometry during mitotic progression is lacking. Here, we use volume electron microscopy to map, with nanometer precision, chromosomes from prometaphase through telophase in human RPE1 cells. During prometaphase, chromosomes acquire a smoother surface, their arms shorten, and the primary centromeric constriction is formed. The chromatin is progressively compacted, ultimately reaching a remarkable nucleosome concentration of over 750 µM in late prometaphase that remains relatively constant during metaphase and early anaphase. Surprisingly, chromosomes then increase their volume in late anaphase prior to deposition of the nuclear envelope. The plateau of total chromosome volume from late prometaphase through early anaphase described here is consistent with proposals that the final stages of chromatin condensation in mitosis involve a limit density, such as might be expected for a process involving phase separation.

中文翻译：

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有丝分裂染色体中从前中期到后期的核小体浓度接近毫摩尔。


染色体压缩是有丝分裂的关键特征，对于准确的染色体分离至关重要。然而，缺乏有丝分裂过程中染色体几何形状的精确定量分析。在这里，我们使用体积电子显微镜以纳米精度绘制人类 RPE1 细胞从中期到末期的染色体图谱。在前中期，染色体获得更光滑的表面，它们的臂缩短，并形成初级着丝粒缢缩。染色质逐渐压缩，最终在前中期达到超过 750 µM 的显着核小体浓度，在中期和早期后期保持相对恒定。令人惊讶的是，染色体在核膜沉积之前的后期后期体积增加。这里描述的从前中期晚期到后期早期的总染色体体积的平台与有丝分裂中染色质浓缩的最后阶段涉及极限密度的提议一致，例如对于涉及相分离的过程可能预期的。