Competitive repopulation assays with TGF-β1^−/− E14 FL cells show defects in hematopoietic repopulation. (A) 5 × 10⁶, 1 × 10⁶, 5 × 10⁵ male E14 FL TGF-β1^+/+ (wt-5, wt-1, and wt-0.5, respectively) or TGF-β1^−/− (KO-5, KO-1, and KO-0.5, respectively) cells were mixed with 1 × 10⁶ female BM cells and transplanted into lethally irradiated CF-1 × Sv129 mice. Graphs represent the percentage of donor-derived cells (percentage of Y) in peripheral blood (PB) of reconstituted mice at 6 weeks, 12 weeks, and 24 weeks after injection (6 mice per group); *P < .05. An example of 2 independent experiments is shown. The contribution of donor-derived cells to each lineage is determined by analyzing the percentage of chromosome Y in the PB of reconstituted mice. (B-D) Total E14 FL cells from TGF-β1^+/+ and TGF-β1^−/− mice were stained with CFSE dye as described in “In vivo homing assay.” CFSE⁺ cells were injected in lethally irradiated mice (15 × 10⁶/mouse). Recipients were killed 3 and 24 hours after injection. Peripheral blood (B), BM (C), and spleen (D) were harvested, and the percentage of homed CFSE⁺ cells was analyzed by flow cytometry. Shown ae flow cytometric profiles for a representative analysis and histograms showing the mean ± SD of 3 independent experiments with 4 mice per experiment (*P < .05). (E) Percentage of CFSE⁺ Lin⁻ cells in BM. Irradiated mice were injected as above and killed 3 hours after injection. Cells were stained with antibodies against lineage markers, and CFSE⁺ Lin⁻ cells were analyzed by flow cytometry. The histogram represents the mean ± SD of 3 independent experiments with 4 mice per experiment (*P < .05).