Fig. 5. Podosomes are more stable and more individualised on rigid substrates. Podosome rosette observed by confocal microscopy for actin GFP in a 3T3 cell seeded on rigid (A) and flexible substrate (B). The 3D reconstruction was made by measuring fluorescence density. High-density regions were coloured in red whereas weaker densities were coloured in green. The rosette on the rigid substrate is composed of individual actin dots covered by a weak actin cloud. (B) When seeded on flexible substrate, the rosette appears more blurred and actin dots are very difficult to distinguish from the denser actin cloud. Bars, 10 µm. (C) Line scan of the fluorescence profile of FITC beads when spread on polyacrylamide gels, allowing the computation of the width at half height of the main peak. (D) Mean width for glass and flexible substrates illustrates the optical diffusion caused by the gel (n=20).