MCAK depletion results in transient long spindles after monastrol washout. (A) A cell treated with control siRNA. (B) A cell treated with MCAK-specific siRNA (arrowheads highlight centrosome position in long spindle). (C and D) Cells treated with control siRNA (C) or MCAK-specific siRNA (D) labeled with antitubulin and antipericentrin. Microtubule length can be measured in live cells expressing GFP-EB3 (green) and RFP-pericentrin (red). (E and F) The longest visible microtubule ends were measured in control (E) or MCAK siRNA-depleted (F) cells from the EB3-labeled tips (open arrowheads) to the center of the centrosomes (black asterisks). (G) Cell means of microtubule length in monasters in control siRNA and MCAK siRNA-depleted live cells. MCAK-depleted cells possess microtubules that are significantly longer (P < 0.001). Error bars correspond to SEM of cell means of the longest measurable microtubules. Bars, 10 µm.