Cell elongation during segregation of long chromatids does not affect cleavage furrow ingression but is associated with a broader cortical myosin distribution. (a) Time-lapse images of control (Video 4) or I-CreI (Video 5) neuroblasts expressing H2Av::RFP (H2Av, cyan) and RLC::GFP (myosin, red). The top panels are merges of maximum projections of deconvolved H2Av and myosin signals. The bottom panels are DIC images. The outline of the cell is shown as a white broken line. In I-CreI cells, cortical myosin starts spreading beyond the cytokinetic ring 4 min after anaphase onset. In addition, pseudocleavage furrows form later during cytokinesis, bracketing the main cytokinetic furrow (red arrowheads). Time is given in minutes:seconds. 0 = anaphase onset. (b) Graph showing the rate of constriction of the myosin ring for control and I-CreI cells. The diameter of the ring is measured from anaphase onset (time = 0 min) to the end of cytokinesis. (c) Localization of myosin during cytokinesis, 4 min after anaphase onset for control and I-CreI cells. The top panels show maximum projections of deconvolved H2Av::RFP signal. The cyan arrows show the positions of the long chromatids. The bottom panels show maximum projections of deconvolved myosin signal. Red arrowheads point to the multiple myosin rings. Bars, 8 µm. (d) The panels show one sagittal plane of myosin nondeconvolved images from control and I-CreI cells. Bars, 8 µm. The graphs show cortical pixel intensity of myosin around one half of the cell cortex, from the GMC cortical pole to the neuroblast cortical pole as delineated by the broken white line in the picture. Note that the distribution curve of the cortical myosin signal is wider and shifted toward the GMC in the I-CreI cell (broken red lines) compared with the control cell (solid red lines).