Effect of Rho inhibition on fibronectin-mediated cellular self-assembly. FN-null MEFs were seeded (2 × 104 cells/cm2) onto tissue culture plates pre-coated with 200 nM (A, B) or 400 nM (C-F) FNIII1HRGD, in the presence of either 10 μM Y-27632 (B, D, F) or an equal volume of the vehicle, PBS (A, C, E). At 4 h post-seeding, cells were treated with 25 nM soluble fibronectin (+sFN) and incubated for up to 3 d. At 72 h post-seeding, phase contrast microscopy images were obtained (A-D). At 24 h post-seeding, some wells were processed for immunofluorescence microscopy and fibronectin fibrils were visualized using polyclonal anti-fibronectin antibodies (E, F). Images represent 1 of 3 experiments performed. Scale bars, 50 μm.