MPD phenotypes induced by Ptpn11^D61G/+ mutation are substantially attenuated by deletion of Gab2. Ptpn11^D61G/+ mice were used to cross Gab2^+/− mice to generate Ptpn11^D61G/+/Gab2^+/− mice. The double heterozygous mice were then intercrossed to produce WT, Gab2^−/−, Ptpn11^D61G/+, and Ptpn11^D61G/+/Gab2^−/− mice. These mice were analyzed at 5-7 months after birth. WBC counts (A; n = 10-13), spleen weights (B; n = 5-8), and percentages of Mac-1⁺ and Gr-1⁺ cells in BM (C; n = 4-10) were determined. Spleens were photographed using a Canon PowerShot SD600 digital camera. (D) BM cells (2 × 10⁴ cells/mL) freshly harvested from 4 genotypes of mice were assayed for colony forming units (CFUs) in 0.9% methylcellulose Iscove Modified Dulbecco medium containing 30% FBS, glutamine (10^-4 M), β-mercaptoethanol (3.3 × 10^-5 M), and IL-3 (D) or GM-CSF (E) at the indicated concentrations. After 7 days of culture at 37°C in a humidified 5% CO₂ incubator, hematopoietic cell colonies (primarily CFU-GM) were counted under an inverted microscope. Experiments described in panels D and E were performed 3 times and similar results were obtained in each. Results shown are the mean ± SEM of triplicates from 1 experiment. P values for comparisons between Ptpn11^D61G/+/Gab2^−/− and Ptpn11^D61G/+ mice were determined by Student t tests. Statistical significance among 4 groups in all panels was verified by 2-way ANOVA followed by Bonferroni or 1-way ANOVA followed by the Tukey posttest.