Competitive transplantation reveals diminished hematopoietic repopulating ability of GATA-2^+/– bone marrow. Male bone marrow nucleated cells from each genotype were admixed in a 1:1 ratio and injected into the lateral veins of warmed female wild-type recipients that had received 10 Gy whole body irradiation. After 7 weeks, nucleated marrow cells from recipients were analyzed in long-term culture initiating cell (LTC-IC) and CFC assays. Discrete colonies derived from week-6 LTC-IC (stem-cells) and day-10 CFC (progenitor) assays were microisolated, lysed, and analyzed by genotyping PCR for the GATA-2 mutant and GATA-2 wild-type alleles. Nucleated marrow cells from recipients were similarly analyzed by CFC assays at 4 and 8 months after transplantation. There were 10 to 15 LTC-IC or CFC colonies screened per transplant recipient. Representative GATA-2 mutant allele PCR from cell lysates of LTC-ICs and CFCs from one recipient animal is shown (A). The mean percentage distribution of stem-cells (LTC-ICs) and progenitor cells (CFCs) from each genotype at 7 weeks after transplantation (LTC-ICs: P < .05, SEM = ± 9.3% for each genotype, n = 6 recipients; CFCs: P < .05, SEM = ± 10.5% for each genotype, n = 6 recipients) (B) and of progenitor cells at 4 and 8 months after transplantation (4 months: P < .05, SEM = ± 4.9% for each genotype, n = 6 recipients; 8 months: P < .05, SEM = ± 5.6% for each genotype n = 6 recipients) (C) are shown, with □ representing wild-type and ▪ the GATA-2^+/– genotypes, respectively. Statistical analysis was performed using the Student t test.