Inhibition of Aurora B by AZD1152-HQPA induces a chromosome segregation defect in mitotic and endomitotic MKs. (A) MKs were stained for tubulin (α and β, green), Aurora B (red), and DNA (blue). (Ai) In MK from untreated cultures, Aurora B accumulated in the midzone of multipolar endomitosis. (Aii) After AZD1152-HQPA treatment Aurora B localized in centromeres of segregating chromosomes. (B) The figure summarizes the percentage of MK mitosis abnormalities after incubation with AZD1152-HQPA: 52% cells were blocked in metaphase/anaphase, 23% in telophase/cytokinesis, 25% in normal mitosis; for multipolar endomitosis we did not find the telophase after incubation with AZD1152-HQPA. (C) Time-lapse images of H2B-GFP–expressing MKs were obtained by confocal video microscopy. Time relative to the first image is indicated in minutes on each image. (Ci) Endomitosis of control cell (8N, 4 poles) from metaphase to telophase. (Cii) Endomitosis of cell treated with AZD1152-HQPA (8N, 4 poles): metaphase, anaphase with slightly segregated chromosomes, and absence of telophase. Scale bars represent 10 μm.