Fig. 1. Formation of focal complexes (FX) and their development into focal adhesions (FA). Porcine aortic endothelial cells were transfected with GFP-ß₃-integrin and cultured to confluence. The monolayer was scratched, creating a `wound' and time lapse movies of transfected cells, migrating into the `wound', were made at 1-minute intervals between exposures (see also Movie 1: http://jcs.biologists.org/supplemental/). For easier visualization of the dynamic process captured in this movie we superimposed sequential `current' and `current + 1 minute' images and colored them red and green, respectively. Structures appearing yellow remained unchanged between the two time points; structures in green are new, and structures in red disappeared before the second exposure. Notice that until 7 minutes there is active protrusion, followed by retraction (until 13 minutes), and the sequence ends with the beginning of a new protrusion. During the protrusive phase every minute new FX are formed, while 1- to 2-minute-old complexes tend to fade and disappear. Upon retraction, most of the FX disappear (in solid line oval) while a few FX grow into FA (dashed line oval). The growing FA expands towards the cell center. Scale bar: 5 µm.