Cell front migrating into labeled collagen during branching morphogenesis. Leader cell protruding into the surrounding collagen matrix from an shControl acinus stimulated with 20 ng/ml HGF for 24 h. GFP-LifeAct (cyan), mCherry-MLC (magenta), and Alexa Fluor 647–labeled collagen (yellow) were imaged at 3-min intervals for 3 h. Time is indicated in h:min. See also Fig. 7 A. Frame rate, seven frames per second; playback, 21 min/s.
