Figure 7.

Polar Ejection Forces on Chromosome Arms Ensure Mitotic Fidelity but Are Not Implicated in the Observed Missegregation Bias for Chromosomes with Large Kinetochores

(A) Live-cell imaging of Indian muntjac fibroblasts stably expressing H2B-GFP to visualize the chromosomes (green) in control (top) and Kif4a RNAi (bottom) cells treated with 50 nM SiR-tubulin to label spindle microtubules (magenta). Scale bar, 5 μm. Time, hr:min. White arrows point to the chromosome arms facing the spindle poles.

(B) Western blot to monitor Kif4a levels after RNAi. GAPDH was used as loading control.

(C) Chromosome missegregation after Kif4a RNAi (fixed cells). Kinetochores (anti-ACA), α-tubulin, and DNA (DAPI) are indicated. Scale bars, 5 μm.

(D and E) Comparison of the frequency of anaphase cells with lagging chromosomes in live (D) and fixed (E) material after Kif4a depletion and/or monastrol washout.

(F) Frequency of anaphase cells with at least 1 lagging chromosome with small or large kinetochores after monastrol washout in Kif4a-depleted fibroblasts. Dashed bar represents theoretical values for frequencies of lagging chromosomes with small kinetochores if the probability to lag was equal for chromosomes with small or large kinetochores.

See also Video S7.