Progenitor assays from chimeric mice. Bone marrow cells from individual WT (n = 9), KO (n = 9), and 9:1 (KO/WT) chimeric (n = 8) mice were plated in methylcellulose with (solid bars) and without (dotted bars) G418 (1 mg/mL) and cultured in conditions supporting the growth of BFU-E, CFU-mixed, or CFU-pre-B colonies. The number of colonies is reported per mouse femur. Cultures of wild-type and KO cells served as controls to confirm the ability of G418 to selectively inhibit the growth of wild-type colonies. Data represent the mean ± SD.