Fig. 2. FAK-null cells have altered FN allocation and organization. (A) Staining of confluent live cells showed highly organized matrix on the dorsal surface of FAK^+/+ cells. FAK^-/- cells had almost no detectable organized fibrillar matrix at the dorsal surface. Stable reintroduction of FAK into these cells (DA2 cells) rescued matrix organization to normal. (B) FN deposits (red) followed cell-cell boundaries in confluent cultures of FAK^-/- cells, as visualized with ß-catenin immunostaining (green). (C) Length distribution of FN trails left behind by migrating cells. There is a higher frequency of short FN fibrils left behind migrating FAK^-/- cells. Length of fibrils was measured using a 1 µm grid laid over immunostained FN trail of migrating cells.