Figure 7

Fibronectin degradation corresponds with podosomes. (A) Microglia labeled with the podosome ring component, talin, showing two large clusters of podosomes (arrows). The cell at the right has a large ring of talin (a podonut). Fibronectin degradation (as in Figure 6) is indicated by loss of fluorescence (note: for better contrast, the AlexaFluor 488 was pseudo-colored as blue). Scale bar: 10 μm. (B) Co-localization of podosomes labeled for F-actin (phalloidin, red) with punctate regions of reduced fibronectin, labeled with AlexaFluor 488 (green). Left: combined phase-contrast and fluorescence image of the front of a microglia (nucleus is smooth circle), stained for F-actin (phalloidin), showing the podosome-rich lamella (boxed area). The colored images of the boxed area show F-actin, and the merged image with AlexaFluor 488-labeled fibronectin. Scale bar: 5 μm. (C) Fibronectin loss is not by phagocytosis. A high-resolution, deconvolved three-dimensional projection shows that punctae of fibronectin staining (green) are adjacent to the glass, rather than inside the microglia (4′,6-diamidino-2-phenylindole-stained nuclei, DAPI, blue). Scale bar: 10 μm.