Spontaneous symmetry breaking and motility initiation of keratocytes. Phase-contrast time-lapse video of a keratocyte spontaneously breaking symmetry and initiating motility. The cell has been reoriented such that the eventual direction of movement is to the right. 50x real time (frames were collected at 5-s intervals and are displayed at 10 frames/s). Cells were imaged in culture media (Leibovitz's L-15 medium without phenol red supplemented with 14.2 mM Hepes, pH 7.4, 10% FBS, and 1% antibiotic-antimycotic). Corresponds to Fig. 2 A (cell B) and video 4 in JCB 178:1207-1221, 2007.