Fig. 7. Microtubules are required for GFP-ninein speckle dynamics. (A) Two image frames (inverted) of the centrosome region taken from a time-lapse series of a GFP-ninein-expressing PtK2 cell treated with nocodazole (see supplementary material Movie 6) showing no positional changes in the speckles. The arrow highlights one of the speckles. Time is shown in seconds (s). Scale bar: 2 µm. (B) Quantitative analyses of GFP-ninein speckle velocities for movements away from the centrosome in control (C) PtK2 cells (0.53±0.06 µm/second, n=27) and in PtK2 cells pre-treated with nocodazole (NOC) (0.09±0.05 µm/second, n=22) or latrunculin B (LB) (0.58±0.06 µm/second, n=36) and towards the centrosome in control (C) (0.37±0.05 µm/second, n=23), nocodazole (NOC) (0.04±0.02 µm/second, n=21) and latrunculin B (LB) treated (0.43±0.04 µm/second, n=35) cells. The results show that only nocodazole is able to significantly (P<0.001) inhibit ninein speckle movements both to and from the centrosome, indicating that microtubules and not actin filaments are required for speckle dynamics.