Wip1 deficiency promotes the development of neutrophils in a p53-independent manner but increases the expression of granulopoiesis-related transcription factors and p38 MAPK-STAT1. (A) BMCs of WT and Wip1KO mice were lysed and analyzed for the expression of Wip1 and p53 by immunoblotting. Data are representative of 3 independent experiments. (B) Representative FACS analysis of peripheral blood and BM CD11b⁺Ly6G⁺ neutrophils from WT, Wip1^−/−, p53^−/−, and p53^−/−Wip1^−/− were shown; represented is 1 of 3 independent experiments with similar results. (C) Erythrocyte-depleted BMCs of WT and Wip1KO mice were treated with G-CSF for the indicated time. Cells were lysed and analyzed by immunoblotting for the phosphorylation of p38 MAPK (p-p38), Erk (p-ErK), STAT1 (p-STAT1), STAT3 (p-STAT3), and S6 (p-S6), as well as for the total amount of proteins used for analysis. (D) Activation of p38 MAPK, STAT1, and Erk in sorted WT and Wip1KO GMPs stimulated with medium alone or G-CSF, assessed by FACS with phosphorylation-specific antibodies. (E) BM neutrophils of WT and Wip1KO mice were lysed and analyzed for the transcriptional factor expression of PU.1, GATA-1, and C/EBPα, β, and ϵ by immunoblotting. Three mice in each group were assayed. The averages of the relative OD value were summarized (right panel). **P < .01, compared with WT mice. (F) The expression of PU.1 and C/EBPα in GMPs of WT and Wip1KO mice was analyzed by FACS.