Pk1 knockdown impairs rear-end retraction. (A) From Video 6. Separating cells in WT (mb-RFP) and Pk1-MO (mb-RFP and LifeAct-GFP) PCM. BCR to the right. In WT, cell–cell contact shrinks (arrows). In Pk1 morphant, F-actin accumulates in retraction fiber and eventually recoils within membranes (arrows). Scale bars, 10 μm. (B) WT and Pk1-MO PCM explants showing morphology and arrangement of mb-RFP– and LifeAct-GFP–labeled cells. BCR is to the right. In Pk1 morphant, F-actin free membrane tethers (white arrows) and F-actin filled retraction fibers (yellow arrows) connect former front–rear cell neighbors. Scale bars, 10 μm.