Tek2 siRNA blocks the formation of the midbody and completion of cytokinesis. (A) Frames from video microscopy sequence of CHO cells expressing a Tek2 siRNA construct targeting the ORF. Two cells enter and exit mitosis, initiate cytokinesis, and then fail cytokinesis and fuse together (arrows). Time is in h:min. (B) siRNA of Tek2 depletes both Tek2 protein and Tek2 mRNA. (C) Tek2 siRNA induces binucleate CHO cells. The mean percentage of binucleate cells for untransfected cells and cells transfected with siRNA constructs targeting the ORF, UTR, or SCR ORF is shown. 100 cells per experiment; n = 3. Error bars are SEM. (D) Tek2 siRNA prevents the formation of the midbody matrix. Cells are linked by overlapping microtubules that lack the central Flemming body (insets). Overlapping microtubules lack Tek2 label; however, Tek2 still decorates the spindle poles, presumably because Tek2 at the centrosome is resistant to degradation. Tek2 forms around the midbody in SCR-expressing cells. Arrows represent Tektin localization. The bottom right inset shows the central midbody (left arrow). Bars, 10 μm.