An F-actin network supports nuclear separation. (A, left) Overlay fluorescence microscopy images of actin (red) and microtubules (green) during nuclear separation in extract. (right) Heat map of the red channel showing actin concentrating in the spindle and asters. (B) Two examples of confocal microscopy time-lapse images of nuclear division while actin filament turnover was inhibited using latrunculin A. (A and B) DNA is in red, and microtubules are in green. Time is shown in minutes/seconds. Bars, 5 µm. (C) Inhibiting actin filament turnover reduced final separation distance (black lines) by significantly (P < 0.001) slowing down postanaphase movement of daughter nuclei, whereas chromosome segregation in anaphase is unaffected (P = 0.111). Each curve represents an independent experiment (gray; from Fig. 1 E). (D) The aster size in latrunculin A–treated extract (black; n ≥ 20, representative out of three repeats) was essentially as in untreated extract (gray; from Fig. 1 G).