Fig. 4. Localization of FN matrix, actin cytoskeleton and ß1 integrin. Cells were cultured for 72 hours to allow matrix assembly and stained using a monoclonal antibody specific for activated ß1 integrin. FN-yfp, cfp-Moe and ß1 images were superimposed. The integrin is prominently localized in spots or small streaks at the ends of actin filament bundles (arrows). Colocalization is sometimes indicated by a yellow color, but because of the variable intensity of fluorescence some FN colocalized with actin appears green (e.g., the FN fibrils indicated by the arrows in a and d). Bar, 20 µm.