Chong Megan K, Rosas-Salvans Miquel, Tran Vanna, Dumont Sophie
Tetrad Graduate Program, UCSF, San Francisco, CA 94158, USA.
Department of Bioengineering & Therapeutic Sciences, UCSF, San Francisco, CA 94158, USA.
bioRxiv. 2023 Oct 18:2023.10.16.562637. doi: 10.1101/2023.10.16.562637.
Accurate chromosome segregation requires sister kinetochores to biorient, attaching to opposite spindle poles. To this end, the mammalian kinetochore destabilizes incorrect attachments and stabilizes correct ones, but how it discriminates between these is not yet clear. Here, we test the model that kinetochore tension is the stabilizing cue and ask how chromosome size impacts that model. We live image PtK2 cells, with just 14 chromosomes, widely ranging in size, and find that long chromosomes align at the metaphase plate later than short chromosomes. Enriching for errors and imaging error correction live, we show that long chromosomes exhibit a specific delay in correcting attachments. Using chromokinesin overexpression and laser ablation to perturb polar ejection forces, we find that chromosome size and force on arms determine alignment order. Thus, we propose a model where increased force on long chromosomes can falsely stabilize incorrect attachments, delaying their biorientation. As such, long chromosomes may require compensatory mechanisms for correcting errors to avoid chromosomal instability.
准确的染色体分离需要姐妹动粒双定向，即附着于纺锤体的两极。为此，哺乳动物的动粒会破坏错误的附着并稳定正确的附着，但它如何区分这两者尚不清楚。在这里，我们测试动粒张力是稳定线索的模型，并询问染色体大小如何影响该模型。我们对仅有14条染色体且大小差异很大的PtK2细胞进行实时成像，发现长染色体比短染色体在中期板上对齐的时间更晚。富集错误并对错误校正进行实时成像，我们发现长染色体在纠正附着方面表现出特定的延迟。使用过表达染色体驱动蛋白和激光消融来干扰极向弹射力，我们发现染色体大小和臂上的力决定了对齐顺序。因此，我们提出了一个模型，即长染色体上增加的力可能会错误地稳定错误的附着，延迟它们的双定向。因此，长染色体可能需要补偿机制来纠正错误，以避免染色体不稳定。
