p53 prohibits propagation of chromosome segregation errors that produce structural aneuploidies

Short summary: The presence of an abnormal karyotype has been shown to be profoundly detrimental at the cellular and organismal level, but is an overt hallmark of cancer. Aneuploidy can lead to p53 activation and hereby prevents proliferation, but the exact trigger for p53 activation has remained controversial. Here, we have used a system to induce aneuploidy in untransformed human cells (RPE-1) to explore how cells deal with different segregation errors. We show that in p53 is activated only in a subset of the cells with an altered chromosome content. Also, we show that at least a subset of whole chromosome aneuploidies can be propagated in p53-proficient cells, indicating that aneuploidy does not always lead to activation of p53. Importantly, we find that propagation of structural aneuploidies (gain or loss of part of a chromosome) induced by segregation errors is limited to p53-deficient cells. Sample collection protocol: RPE-1 (WT or p53 KD) cells were treated with an Mps1 and CENP-E inhibitor collected either in bulk, or by microscopic selection of cells containing micronuclei. Cells were stored in medium with 10% DMSO at -80C until sorted. Prior to sorting, cells were thawed, and incubated in the dark on ice for at least 10 minutes in a DNA-staining buffer containing 10ug/mL PI and 10ug/mL Hoechst (for full description, see Bakker et al., 2016, Genome Biology 17:115 and Van den Bos et al., 2016, Genome Biology 17:116). Separation of cycling G1 cells in the BrdU-experiment was performed using Hoechst-quenching (Falconer et al., 2012, Nature Methods, 9:1107-1112). Nucleic acid library construction protocol: Library preparation was performed using a modified Strand-seq protocol (Van den Bos et al., 2016, Genome Biology 17:116), which excludes the BrdU incorporation and UV-treatment , using a Bravo Automated Liquid Handling Platform (Agilent Technologies, Santa Clara, USA). Libraries were then size selected and pooled. Nucleic acid sequencing protocol: Libraries were sequenced on an Illumina HiSeq 2500 or NextSeq 500 sequencer.