Hematopoietic progenitor cells in SrfKO^H fetal liver. (A) Cellularity of SrfKO^H and Srf⁺ fetal liver. (B) Fetal liver LSK cells (see also supplemental Figure 1B). Panels Bi-ii, elevated numbers of LSK cells in SrfKO^H fetal liver. Panel Biii, BrdU labeling indicates that SrfKO^H LSK cells are more proliferative than those from Srf⁺ embryos. (C) Similar proportions of CD150^hi cells in SrfKO^H fetal liver. (D) SrfKO^H and Srf⁺ fetal liver cells generate similar numbers of colonies in colony-formation assays. Data are from 6 Srf⁺ and 4 SrfKO^H embryos; each assay was performed in triplicate. See supplemental Figure 1C. (E) Although SrfKO^H and Srf⁺ colony morphologies are different (i), the total cell numbers are similar (ii).