Fig. 4. Rac1^–/– BMMs have a reduced ruffling response to CSF-1. CSF-1-starved (A,B) and CSF-1-stimulated BMMs (C,D) were fixed and stained for F-actin with TRITC-phalloidin. Arrows indicate membrane ruffles. (Inset) An example of a Rac1^–/– BMM that has a full ruffling response to CSF-1. Scale bar: 10 µm. (E,F) Quantification of changes in adhesive area (E) and cell elongation ratio (ratio of the longest to the shortest cell axes; F) in growing, starved and CSF-1 stimulated WtCre and Rac1^–/– BMMs. The results shown are mean±s.e.m. of 100 cells from each population over two separate experiments. Statistical significance compared to WtCre growing values was calculated using Student's t-test, ^*P<0.05; ^***P<0.001.