Time-lapse confocal microscopy of a live thrombin-stimulated iMK reveals bending and displacement of fibrin fibers caused by the contracting plasma membrane protrusions. (A) A representative image of a thrombin-stimulated iMK (1 of 11 individual iMKs analyzed) embedded into the fibrin network of a contracting plasma clot. Arrows indicate 2 blebs and a filopodium attached to and pulling on the fibrin fibers. Scale bars, 10 μm. (Top panel) combined fibrin and iMK images; (middle panel) iMK only; (bottom panel) fibrin network only. (B-C) Zoomed images of the contracting blebs (B) and a filopodium (C) indicated in panel A at different time points, showing retraction of the plasma membrane that induces bending and displacement of the attached fibrin fibers. White dashed lines indicate the initial profiles of the iMK emerged protrusions (middle panels) or fibrin (bottom panels). Scale bars, 2 μm. See supplemental Video 3 for the full sequence.