Enforced miR-34a expression enhances MK differentiation of human CD34⁺hematopoietic precursors. (A) CD34⁺ hematopoietic cells, differentiated to MK by culture in medium containing TPO, SCF, and IL-3, express MK integrins. The proportion of CD41/CD61-positive cells is indicated. (B) Changes in miR-34a and its MYB, CDK4, and CDK6 target mRNAs were evaluated by quantitative PCR. miR-34a expression is normalized to U6 and mRNA is normalized to GAPDH. Gene expression is plotted as expression relative to day 0. ND indicates not detected. (C) CFU-MK assay of miRNA-overexpressing CD34⁺ HSCs. Primary human CD34⁺ cord blood cells were infected with lentiviruses encoding the indicated miRNAs, and the effect of miRNA overexpression on CFU-MK numbers was evaluated 12 days later. The bar graph represents the mean ± SD of quadruplicate samples. A representative experiment of 3 independent experiments is shown. #P < .05 relative to control lentivirus-infected cells. Exogenous miR-34a and miR-150 both enhance MK colony numbers.