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Nuclear chromosome locations dictate segregation error frequencies

Chromosome segregation errors during cell divisions generate aneuploidies and micronuclei, which can undergo extensive chromosomal rearrangements such as chromothripsis [1, 2, 3, 4, 5]. Selective pressures then shape distinct aneuploidy and rearrangement patterns—for example, in cancer [6, 7] —but it is unknown whether initial biases in segregation errors and micronucleation exist for particular chromosomes. Using single-cell DNA sequencing [8] after an error-prone mitosis in untransformed, diploid cell lines and organoids, we show that chromosomes have different segregation error frequencies that result in non-random aneuploidy landscapes. Isolation and sequencing of single micronuclei from these cells showed that mis-segregating chromosomes frequently also preferentially become entrapped in micronuclei. A similar bias was found in naturally occurring micronuclei of two cancer cell lines. We find that segregation error frequencies of individual chromosomes correlate with their location in the interphase nucleus, and show that this is highest for peripheral chromosomes behind spindle poles. Randomization of chromosome positions, Cas9-mediated live tracking and forced repositioning of individual chromosomes showed that a greater distance from the nuclear centre directly increases the propensity to mis-segregate. Accordingly, chromothripsis in cancer genomes [9] and aneuploidies in early development [10] occur more frequently for larger chromosomes, which are preferentially located near the nuclear periphery. Our findings reveal a direct link between nuclear chromosome positions, segregation error frequencies and micronucleus content, with implications for our understanding of tumour genome evolution and the origins of specific aneuploidies during development. 1. van Jaarsveld, R. H. & Kops, G. J. P. L. Difference makers: chromosomal instability versus aneuploidy in cancer. Trends Cancer 2, 561–571 (2016). 2. Compton, D. A. Mechanisms of aneuploidy. Curr. Opin. Cell Biol. 23, 109–113 (2011). 3. Zhang, C. Z. et al. Chromothripsis from DNA damage in micronuclei. Nature 522, 179–184 (2015). 4. Ly, P. et al. Chromosome segregation errors generate a diverse spectrum of simple and complex genomic rearrangements. Nat. Genet. 51, 705–715 (2019). 5. Shoshani, O. et al. Chromothripsis drives the evolution of gene amplification in cancer. Nature 591, 137–141 (2021). 6. Davoli, T. et al. Cumulative haploinsufficiency and triplosensitivity drive aneuploidy patterns and shape the cancer genome. Cell 155, 948–962 (2013). 7. Knouse, K. A., Davoli, T., Elledge, S. J. & Amon, A. Aneuploidy in cancer: seq-ing answers to old questions. Annu. Rev. Cancer Biol. 1, 335–354 (2017). 8. Bolhaqueiro, A. C. F. et al. Ongoing chromosomal instability and karyotype evolution in human colorectal cancer organoids. Nat. Genet. 51, 824–834 (2019). 9. Cortés-Ciriano, I. et al. Comprehensive analysis of chromothripsis in 2, 658 human cancers using whole-genome sequencing. Nat. Genet. 52, 331–341 (2020). 10. McCoy, R. C. et al. Evidence of selection against complex mitotic-origin aneuploidy during preimplantation development. PLoS Genet. 348, 235–238 (2015).

Nucleus ; Spindle pole ; Segregation bias ; Aneuploidy

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