Analysis of hematopoiesis in Pitx2^+/+ and Pitx2^–/– fetal liver at 13.5 days after coitus. (A) Histograms show the number of CFCs per 1 × 10³ CD45⁺ Pitx2^+/+ (□) and Pitx2^–/– (▪) fetal liver cells at 13.5 days after coitus. Results represent the mean ± SEM of 4 separate experiments. (B) Multilineage differentiation of donor-derived hematopoietic cells in the bone marrow, thymus, and spleen cells of mice receiving transplants with Pitx2^+/+ (□) and Pitx2^–/– (▪) fetal liver cells. Differentiation marker expression was studied using antibodies specific for mouse antigens TER119 (erythroid cells), Mac1 (CD11-b, macrophages), CD19 (B cells), Gr1 (Ly-6G, granulocytes), CD41 (megakaryocytic cells), and CD4 and CD8 (T cells).