Figure 1: HT-1080 cells expressing promoter-truncated EGFP-paxillin in collagen gels.

HT-1080 cells, expressing promoter-truncated EGFP-paxillin, were cultured in 2 mg ml⁻¹ rat-tail collagen gels (BD Biosciences) and imaged at 18–24 h to determine the percentage of cells with visible adhesions (see original paper for full experimental details). Results were compiled from three independent experiments. (a,b) Representative fluorescence z-projections of HT-1080 cells with visible adhesions (arrows). Bar: main images, 10 μm; insets, 5 μm. (c,d) Percentage of fluorescent HT-1080 cells with at least one visible adhesion, binned according to depth in the gel or to the relative intensity of the protrusion background fluorescence (n = 27 cells; see original paper for details). (e,f) The same quantifications were performed on cells in gels made from rat-tail collagen from Life Technologies (n = 23). Cells with visible adhesions were observed at depths up to the limit of the working distance of our objective (∼300 μm).