Fig. 5. Failure of cells defective in calpain to respond to the engagement of dorsal integrins. Capn4^–/– (B,D) or rescued (A,C) fibroblasts were cultured on the surface (A,B), or within two layers (C,D), of fibronectin-coated polyacrylamide substrates. Only rescued cells respond to the engagement of dorsal integrins by adopting an elongated shape. Scale bar: 10 µm. The response is quantified by taking the ratio of the length to the width of cells (E). In addition, similar results are obtained with siRNA-induced gene silencing using NIH3T3 cells. Each bar represents mean ± s.e.m. of 25 cells from three experiments.