(A) Proof-of-principle experiment. Time-lapse images show overexpression of Myc-tagged CPAP-WT (i) or CPAPΔT (ii) has no effect on two centrosome-containing MCF10A cells (-Dox, two centrosomes). The cells were imaged from interphase to Cytokinesis. Bar graph at right quantifies mitotic duration of cells overexpressing CPAP-WT and CPAPΔT. We define mitotic duration as time consumed from the onset of cell rounding until cytokinesis. Number of cells (n) analyzed in each condition is indicated at the top of each bar. Number of independent experiments (N), (N)=3. Error bars, mean ± SEM. Unpaired t-test. CPAP-WT (iii) or CPAPΔT (iv) expressing extra centrosome-containing MCF10A cells (+Dox, extra centrosomes). Note compared to CPAP-WT expressing centrosomes (iii) CPAPΔT expressing centrosomes nucleate enhanced levels of microtubule asters already at prophase-like stage (iv). White arrows indicate centrosomal dots. Red arrows indicate centrosomes nucleating microtubule asters causing multipolar spindles. Scale bar, 2µm. Bar graph at right quantifies mitotic duration and percentage of cells exhibiting prolonged mitosis in cells expressing CPAP-WT and CPAPΔT. (N)=3. Error bars, mean ± SEM. Unpaired t-test ***P < 0.0001 