E12.5 Sp3-deficient fetal liver cells show reduced in vivo hematopoietic reconstitution. Analysis of the peripheral blood for lacZ-expressing cells at 6 weeks after transplantation in the indicated cell lineages in peripheral blood from mice that received Sp3^+/- (•) or Sp3^-/- (○) fetal liver cells. The mean number of injected cells per recipient was 2.6 × 10⁵ (0.41 ± 0.17 embryo equivalents) for Sp3^+/- fetal liver cells and 2.1 × 10⁵ (0.58 ± 0.13 embryo equivalents) for Sp3^-/- fetal liver cells. Fetal liver cells from 10 of 11 Sp3^+/- embryos and 4 of 7 Sp3^+/- embryos were transplanted into 2 mice, and in these cases the symbols show the average values in the 2 mice. In the other cases, the symbols represent the values in individual mice. Only recipients with more than 10% lacZ⁺ cells are considered positive. For comparison, the proportions of lacZ expression in 3-month-old Sp3^+/- heterozygous mice are indicated (approximately 70% in T and NK cells, approximately 80% in monocytes, and approximately 90% in B cells and granulocytes, values that would therefore reflect 100% engraftment).