Partial inhibition of dynein suppresses rapid directional instability in kinetochore trajectories. (A) Frequency of fast jumps in kinetochore trajectories. Error bars are 95% confidence intervals for binomial distribution. (B) Example of kinetochore movement patterns during anaphase in an RPE1 cell. K1 moves monotonically (directionally stable), whereas K2 exhibits periods of rapid poleward movement intermittent with directional reversals. Arrows mark periods when poleward velocity exceeds 6 µm/min. Top panel presents a raw kymogram. In the bottom panel, movements of each kinetochore are shown with respect to its connected centrosome. C1 and C2, centrosomes; K1 and K2, sister kinetochores. (C) Spindle organization in control (top row) versus 10 µM Ciliobrevin-treated RPE1 cells. Notice separation of the centrosomes from the spindle poles, widening of the spindle poles (arrows), and exaggerated presence of peripheral MTs in the drug-treated cell. Arrowhead denotes a short K-fiber, not attached to the spindle pole in a Ciliobrevin-treated cell. (D) Example of kinetochore trajectories in an RPE1 cell treated with 10 µM Ciliobrevin for 2 h. Notice decreased poleward velocity (compare slope of the trajectories in B) and monotonous (directionally stable) pattern of kinetochore movements.