The effect of the actin cytoskeleton on mitosis after culture on 2D square patterned substrates.

<p>(A) HeLa cells (YFP-paxillin) were cultured on 2D square patterns for 18 hours and imaged during interphase for actin (red) and paxillin (green). HeLa cells (RFP-tubulin/GFP-H2B) were assessed for the angle of the mitotic spindle in the xy plane at metaphase after culture on 2D square patterns and treatment with (B) media or (C) latrunculin A. A high proportion of the cells cultured on square patterns aligned the mitotic spindle along the diagonal of the cell, which was reduced by the addition of latrunculin A. (D) Conversely the addition of latrunculin A had little effect on the average orientation of the mitotic spindle perpendicular to the substrate plane. Values represent spindle angle in degrees ± SEM. (E) Furthermore, the addition of latrunculin A had little effect on the distribution of the spindle orientation. (F) Cells treated with latrunculin A (light grey bars) took significantly less time to progress from late prometaphase to metaphase and to complete mitosis than untreated cells (black bars). All values represent time in minutes ± SEM. Key: *** p<0.001; NB = nuclear envelope breakdown, S = spindle formation, LPM = late prometaphase, M = metaphase, A = anaphase.