Gab2^−/− mouse BM cells are present in normal absolute numbers despite the absence of Gab2 expression. (A) Total BM cells were harvested from individual littermate wild-type and Gab2^−/− mice. The total cellularity is shown for n = 10 wild-type and Gab2^−/− mice. No significant difference was observed (P = .7). (B) BM lysates from wild-type and Gab2^−/− mice were immunoprecipitated with anti-Gab2 antibody and then subjected to Western blot analysis with anti-Gab2 antibody. The antibody used for these studies was provided by Toshio Hirano. IP/WB included positive control ecotropic producer cells expressing Gab2 from the MSCV-Gab2-IRGFP vector. The negative control ecotropic producer cells contained only the MSCV-IRGFP empty vector. Note that the producer cells (3T3-based) expressed some endogenous Gab2; this was increased with the vector containing Gab2. Error bars represent the mean plus or minus a standard deviation.