Fig 1: PLK1 inactivation induces spindle-dependent centromere dislocation. a Experimental outline (top) and representative deconvolved images showing chromosomes isolated from RPE1 cells under the indicated treatment. Chromosomes were hybridised with FISH DNA probes against centromeres (green) and telomeres (red). Left panels: examples of normal chromosome configuration (+nocodazole). Middle panels: examples of BI2536-induced ‘centromere dislocations’ (asterisks; 1–5), ‘partial centromere splitting’ (arrowhead; 3), and a centromere DNA thread linking two separate chromosome arms (connecting arrow; 5). Right panels: chromosomes with ‘partial centromere splitting’ (arrowhead) after BI2536 and nocodazole co-treatment. Note: also see Supplementary Fig. 7 for the whole-chromosome spread images. b Quantification of ‘chromosome arm dislocations’ (left) and ‘partially centromere splitting’ (right) under the indicated inhibitor treatment (n = 3 independent experiments analysing 75 spreads in each condition; the means of each experiment are shown). c A diagram depicting the outcomes of chromosome breakage within or outside centromeres. (i) Breakage at centromeres generates both broken arms (100%) positive for CEN FISH signal; (ii) breakage at pericentric or arm regions generates one of the broken arms (50%) positive for a CEN FISH signal. Quantification (right) of the examined broken chromosome arms with or without centromere FISH signal at their termini (524 broken chromosome arms were scored from 11 separate chromosome spreads showing the highest centromere dislocation frequency). d Experimental outline (top) and mFISH karyotyping of RPE1 cells. BI2536 induced chromosome ‘p’- and ‘q’-arm separation. Note: there is a marker ‘M’ chromosome with a translocation of chromosome X and 10 in RPE1 cells. Bar graph (bottom) showing the frequency of ‘centromere dislocations’ among individual chromosomes. Inset graph showing the positive correlation between chromosome length and ‘centromere dislocation’ frequency (23 spreads were analysed). Note: acrocentric chromosomes were not determined and the length of the ‘marker’ chromosome is unknown. e Condensin (SMC2) is detected on some PLK1-associated DNA threads (arrows). Scale bars = 5 µm. f A model of centromere dislocation induced by PLK1 inactivation in a spindle-dependent manner. Spindle-mediated tension causes decompaction of centromere axis, the formation of centromere DNA threads and whole-chromosome arm separation