Blocking Rac1 activation inhibits plating of islets in vitro. (A,B) Isolated islets were seeded onto gelatin coated tissue culture dishes and incubated for one week. Whereas wild-type islets plate out and show actin remodelling; marked by phalloidin staining of stress fibres (arrows) of leading-edge cells (C), the RIP-RacN17 islets remained intact (B) with minor actin remodelling (D). (E) Quantification of the plating-efficiency of islets after one week in culture showed lower plating-efficiency of transgenic islets compared to wild-type islets (n = 5). Arrowheads in C and D indicate focal contacts and junctional F-actin, respectively. Error bars represent standard deviation from the mean (± s.d.) and significant values are indicated as *p < 0.05 determined by Student's t-test. Bars, 100 μm (A,B) and 20 μm (C,D).