CLASP2 phosphorylation on S1234 is required to maintain mitotic spindle bipolarity. (A and A’) HeLa cell overexpressing GFP-CLASP2 S1234A mutant (green) with a monopolar spindle, immunostained for α-tubulin (red, left), ACA (red, right), and DNA counterstained with DAPI (blue, left). Bar, 5 µm. (B) Quantification of the mean percentage of monopolar spindles in cells overexpressing GFP-CLASP2 wild-type (n = 232), S1234A (n = 341), S1234D (n = 220), S_A Plk1 (n = 215), and S_D Plk1 (n = 220) from three independent experiments. Error bars refer to standard error. One-way ANOVA Bonferroni’s test revealed statistically significant differences indicated with * (P < 0.05). (C) Mitotic spindle collapse of HeLa cells stably expressing mCherry-H2B Histone and transfected with S1234A mutant. GFP-CLASP2 S1234A or wild-type are represented in grayscale in C’. (D) Cell death in HeLa cells arrested in a monopolar conformation upon overexpression of the GFP-CLASP2 S1234A (grayscale in D’). Time is shown in hours:minutes. Bars, 10 µm.