Mesenchymal cells produce fibronectin and assemble it into an insoluble matrix. In vivo, this matrix is vital for adhesion and migration of other cells during development. Here, we used β1 integrin-deficient cells that cannot assemble a fibronectin matrix.

This picture shows that increased expression of β3 cannot restore matrix assembly in these cells (lower left), despite the fact that it restores adhesion to immobilized fibronectin (not shown). By contrast, re-expression of β1 leads to efficient matrix assembly (upper left). The color pictures on the right show localization of tensin (marked in green), a cytoskeletal protein that translocates from “focal adhesions” to another type of adhesion structures termed “fibrillar adhesions” that are associated with fibronectin fibrillogenesis. Again, this translocation occurs when β1 integrin are present (upper right) but not when they are absent (lower right).

By Erik Danen.