Bone marrow colony-forming assays. (A) Whole bone marrow was harvested from wild-type (WT; □) and TC-PTP^−/− (KO; ▪) mice at P1 (3 WT, 3 KO), P4 (2 WT, 4 KO), and P7 (4 WT, 3 KO) and incubated in methylcellulose medium. The total number of colonies per culture dish is reported as mean ± SD. *P < .002. (B) Whole bone marrow was harvested from wild-type (WT; □) and TC-PTP^−/− (KO; ▪) mice at P7 (8 WT, 6 KO). Cells were cultured in methylcellulose medium supplemented with IL-7 in uncoated culture dishes (Ctl BM) or on monolayers of bone marrow stromal cells from WT mice (SC +/+) or KO mice (SC −/−). As control, marrow stromal cells were cultured with methylcellulose medium containing IL-7 without bone marrow cells (Ctl SC). The total number of colonies per culture dish is reported as mean ± SD. *P < .002. (C) Flow cytometry analysis of CFU–pre-B cells recovered from methylcellulose cultures. Analysis was gated on B220⁺ cells (95% B220⁺ for TC-PTP^+/+ and 94% B220⁺ for TC-PTP^−/−) to include only B cells. Representative data are shown for flow cytometry of TC-PTP^+/+ and TC-PTP^−/− cultures. All experiments were repeated at least 3 times.