Figure 3. Internalized cells disrupt cleavage furrow formation.

(a) Graph: duration of cleavage furrow determined by 3D imaging (mean +/− S.D.). Left bar, internalized cells away from cleavage plane, host cells with symmetric furrow (n=11; all divisions successful). Middle and right bars: internalized cells within cleavage plane, host cells with asymmetric furrows (n=19; 13 successful and 6 failed). Successful asymmetric divisions had longer furrow duration than symmetric divisions (*p<.001, Mann-Whitney), and failed asymmetric divisions had longer furrow duration than successful ones (**p=.018, Mann-Whitney). Blue circles in cartoons (below graph) represent internalized cells, and red regions (arrows) represent cleavage furrows. Time-lapse images are shown for symmetric (1) and asymmetric (2,3), and successful (1,2) and failed (3) divisions. Arrows indicate cleavage furrows (See also Movies S6–8). (b) Internalized cells block cleavage furrow formation. Left images: time-lapse of MCF10A-GFP-Tubulin cells from metaphase (top image) to telophase with asymmetric furrow (bottom image) (See Movie S10). Middle image panel: same cell from time-lapse, stained for phosphorylated myosin light chain serine 19 (pMLC-S19) (red), α-Tubulin (green), and nuclei (blue). Note contractile ring (pMLC) only half-formed (white arrow). Main image is 3D reconstruction (axes labeled at bottom left x (green), y (red), z (blue)). Left inset is single x-y plane. Right inset, 3D reconstruction of pMLC-S19 staining shown as grayscale and angled to visualize contractile ring. Right image panel shows normal cell division; main image is 3D reconstruction, left inset is single x-y plane, right inset shows 3D reconstructon of pMLC-S19 staining (grayscale), angled to visualize contractile ring. All bars = 10μm.