Spinning disk confocal time-lapse imaging of mitosis in asynchronous HeLa cells transfected with control, nontargeting siRNA oligonucleotides, or siRNA oligonucleotides targeting HsKNL2. Top, nontargeting siRNA oligonucleotides; bottom, siRNA oligonucleotides targeting HsKNL2. DIC is shown on the left, and YFP-CENP-A is shown on the right. The control cell on the left begins in metaphase and, over the course of the video, completes mitosis successfully. Paired YFP-CENP-A loci oscillate during metaphase and then segregate to opposite poles during anaphase. In the HsKNL2 knockdown cells, YFP-CENP-A is not seen to localize at any point during the video. Two cells begin in metaphase and leave mitosis during the video. The DIC channel shows that chromosomes do not oscillate as seen in controls and, during anaphase, segregate with aberrant poleward movement in the cell on the left and nominal poleward movement in the cell on the right. The video is ∼75 min long, and the frame is ∼40 µm top to bottom. Images were acquired at 60-s intervals).