Frequency of progenitor cells in the spleen and marrow from normal and GATA-1^low mice.

(A) (B) Frequency of progenitor cells (BFU-E, dark bars; CFU-E, dotted bars; and CFU-GM, white bars) in the spleen (panel A) and the bone marrow (panel B) of untreated (steady-state), day-1 PHZ-treated, and day-6 EPO-treated wild-type and GATA-1^low mice. The results are presented as the mean ( ± SD) of 4 separate experiments. Four wild-type and 4 GATA-1^low mice were analyzed for each experimental point (4 untreated, 4 EPO-treated, and 4 PHZ-treated animals for a total of 12 wild-type and 12 GATA-1^lowmice). (C) EPO concentration/response curve on the growth of CFU-E–derived (bottom) and BFU-E–derived (top) colonies in serum-deprived cultures of light-density spleen cells from wild-type (closed circles) and GATA-1^low (open triangles) mice. The results are presented as a percentage of the maximal colony growth and are the mean ( ± SD) of 4 separate experiments. Maximal colony efficiency (100%) was as follows: wild-type BFU-E = 68 ± 22; wild-type CFU-E = 110 ± 30; GATA-1^lowBFU-E = 166 ± 30; GATA-1^low CFU-E = 750 ± 175. Identical EPO concentration/response curves were observed in cultures of marrow cells (not shown).