(A) Adhesion of pKO-β1, pKO-αv and pKO-αv/β1 fibroblasts seeded on pFNwt or pFNsyn for indicated times (n = 3 independent experiments; mean ± sem). (B) pKO-β1, pKO-αv and pKO-αv/β1 fibroblasts were seeded on pFNwt or pFNsyn, fixed at the indicated times and stained for total β1 integrin (green), paxillin (white) and F-actin (red). Scale bar, 50 μm. (C–E) Quantification of cell area of pKO-β1 (C), pKO-αv (D) and pKO-αv/β1 (E) cells seeded on pFNwt or pFNsyn for indicated times. (F–H) Quantification of the number of FAs (F), the percentage of FA coverage measured as paxillin-positive area (G) and the percentage of β1 integrin-positive areas referred to the total cell area (H) in pKO-β1 cells (n = 25 cells for each measurement and three independent experiments; mean ± sem). The binding probability of integrins to FNIII7-10wt or FNIII7-10syn fragments (I) and to full length (fl-FN) pFNwt or pFNsyn (J) determined by single-cell force spectroscopy. Numbers in parentheses indicate events studied for each condition. Statistical significances were calculated using the Student t-test; *p<0.05, **p<0.01, ***p<0.001 and ****p<0.0001.