miR-29a/b-1-null HSPCs exhibit decreased colony forming capacity in methylcellulose colony assays. (A) Methylcellulose colony assays were performed using c-Kit⁺-enriched bone marrow cells. The first plating was initiated using 3000 c-Kit⁺ cells from WT, Het, and KO mice. Replatings were performed using 20 000 cells per well. (B) Photomicrographs of typical colonies generated by WT, Het, and KO HSPCs on initial plating. (C) Methylcellulose colony assays were performed using purified HSPCs. Six populations, including HSC, MPPa, MPPb, CMP, MEP, and GMP, were double FACS sorted and 150 (HSC, MPPa, MPPb) or 400 (CMP, MEP, and GMP) cells were plated. Data shown represent the aggregate of 3 technical replicates. Error bars indicate SEM. Statistical significance was calculated using a Student t test: *P < .05; **P < .01.