Inhibition of poleward microtubule flux in spindles lacking overlapping microtubules at their equator. (A) Representative kymographs of spindles treated as indicated. The vertical axis of the kymograph corresponds to the time line of spindle imaging. The slope of speckle trajectories corresponds to the poleward microtubule flux rate. Bar, 5 μm. (B) Poleward microtubule flux rates measured for spindles assembled in control (ΔIgG) extracts (8 spindles, 2 different extracts, 222 speckle trajectories), ΔEB1 extracts (n = 14 spindles, 2 different extracts, 346 speckle trajectories), and ΔEB1 extracts supplemented either with EB1 (10 spindles, 2 different extracts, 290 speckle trajectories) or a onefold excess of XMAP215 (12 spindles, 2 different extracts, 298 speckle trajectories). Error bars show SD. (C) Representative kymographs of spindles treated as indicated. Bar, 5 μm. (D) Poleward microtubule flux rates measured for spindles assembled in ΔIgG control extracts (n = 8 spindles, 2 different extracts, 281 speckle trajectories), ∼ΔXMAP215 extracts (n = 11 spindles, 2 different extracts, 329 speckle trajectories), and ∼ΔXMAP215 extracts supplemented either with XMAP215 (n = 8 spindles, 2 different extracts, 202 speckle trajectories) or a threefold excess EB1 (n = 11 spindles, 2 different extracts, 354 speckle trajectories). Error bars show SD.

## PubMed Commons