Proliferation and differentiation response of EG-R–expressing bone marrow cells.

(A) Total number of colonies per plate stimulated in response to increasing concentrations of EGF (0-60 ng/mL) in agar was counted on day 4, as described in “Materials and methods.” Colony numbers were corrected for infection efficiency. Data represent the average of 3 independent experiments. (B) Bone marrow cells were incubated in increasing concentrations of EGF (0-60 ng/mL) for 3 days, containing methyl–³H-thymidine for the last 20 hours of culture. Proliferation response was measured in counts per minute (cpm) and was corrected for infection efficiency. This figure is a representative of 2 independent experiments. (C) Proliferation response of bone marrow cells to G-CSF (0-30 ng/mL) as a control was also measured. This figure is representative of 2 independent experiments. WT, (○); Y₇₀₄→F, (●); Y₇₂₉→F, (▴); Y₇₄₄→F, (▾); Y₇₆₄→F, (♦); Y_null, (▪); P_{640, 642}→S, (▵); and vector alone (▿).