Effect of CBFβ dosage on hematopoietic progenitor numbers. (A) CFU-GMs, BFU-Es, and CFU-GEMMs in 12.5-dpc fetal livers. n_+/+ = 14, n_rss/+ = 12, n_+/− = 11, n_rss/rss = 4, and n_rss/− = 4. Asterisks indicate differences from Cbfb^+/+ significant at P = .01. (B) CFU-Cs per 5 × 10⁵ 17.5-dpc fetal liver cells. n_+/+ = 9, n_rss/+ = 7, n_+/− = 9, n_rss/rss = 4, and n_rss/− = 8. Asterisks indicate differences from Cbfb^+/+ significant at P = .01. (C) Megakaryocyte progenitors (CFU-Mk) per 2.2 × 10⁵ 17.5-dpc fetal liver cells. n_+/+ = 10, n_rss/+ = 14, n_+/− = 11, n_rss/rss = 3, and n_rss/− = 6. Asterisks indicate differences between Cbfb^rss/rss and Cbfb^rss/− versus all other genotypes significant at P = .01.