Cytoskeleton and adhesion patterns of cultured chick embryo chondrocytes during cell spreading and Rous sarcoma virus transformation

The cytoskeleton and the adhesion complex of chick embryo chondrocytes maintained in vitro have been studied by fluorescence and interference reflection microscopy during the process of cell spreading. The pattern of actin-containing microfilaments and the distribution of vinculin speckles on adhesion plaques have been found to change as a function of the culture time. Newly plated chondrocytes adhere to the substratum mostly around a peripheral ring-like region and show a complex tridimensional array of microfilaments. When chondrocytes flatten, they develop stress fibres and show a diffuse system of vinculin-containing adhesion plaques scattered over the entire ventral side of the cells. Upon infection with Rous sarcoma virus (RSV) chondrocytes display one or more actin-containing ruffles located on the dorsal side similar to the 'actin flowers' earlier described in other cell types. These structures have been found to accumulate vinculin too. In chondrocytes infected with two td-ts mutants of RSV, 'actin flowers' have been found to persist at the restrictive temperature. At this temperature, however, in the majority of cells, stress fibres and adhesion plaques reappear.