Hematopoietic colonies and long-term repopulation potential of HAT^+/+, HAT^+/−, and HAT^−/− fetal liver cells. (A) Numbers of colonies generated by HAT^+/+, HAT^+/−, and HAT^−/− fetal liver cells from littermate animals. A total of 30 × 10³ cells/mL was replated in methylcellulose medium. Fetal liver cells were then genotyped, and myeloid, erythroid, and mixed lineage colonies were scored after 6 to 8 days. The average of the number of colonies generated is indicated by a horizontal bar. (B) Comparative size of representative HAT^+/+ and HAT^−/− colonies generated from day 14.5 fetal liver (magnification ×100). (C) Competitive long-term repopulation of irradiated mice. Data are expressed in log ratio between tested C57BL/6 fetal liver–derived (CD45.2⁺) and competitor PEP3 bone marrow–derived cells (CD45.1⁺). A total of 2 × 10⁵ fetal liver cells from HAT^+/+, HAT^+/−, and HAT^−/− embryos was transplanted into irradiated CD45.1⁺/CD45.2⁺ recipients with 4 × 10⁵ competitor bone marrow cells from PEP3 mice (CD45.1⁺). A total of 2 × 10⁶ cells from primary recipients was transplanted into secondary recipients 3 months after reconstitution. Bars represent standard error of the mean values. *P < .5; **P < .01; ***P < .005.