Aberrant chromosome segregation and interphase phosphorylation monitored using fluorescent Fab. (A) Anaphase HeLa cells showing aberrant chromosome segregation. Fixed cells were stained with Fab311-488 (red), anti–aurora B (green), and DAPI (blue). Arrows indicate a missegregated chromosome (left) and a chromosome bridge (right). (B) Missegregated chromosomes are readily detectable in living cells using Fab311-555. HeLa cells expressing histone H2B–GFP were loaded with Fab311-555, and images were taken every 3 min. A missegregated chromosome (arrows) is easily visible by Fab311, whereas contrast enhancement is required for detection by H2B-GFP. (C) Frequency of chromosome missegregation and period of Fab311-488 foci appearance before mitosis measured using time-lapse imaging. (left) The chromosome missegregation rate. (right) The period of Fab311-488 foci appearance before mitosis. (D) Time-lapse images of a fibroblast loaded with Fab311-488. H3S10ph focus (arrow) appears >5 h before mitosis, and others appear (arrowheads) later. See Video 7. Bars, 5 µm.