zEpo increases precursor cell survival and differentiation. (A) Epo stimulates precursor survival. Fold change in precursor number after 5 days in culture. Cytokine conditions listed at bottom (n = 3). (B) RT-PCR expression of the zebrafish transferrin-a (tfa) gene in zebrafish tissues. (C) Increased erythroid differentiation achieved by exogenous iron delivery. Percent o-dianisidine-positive erythroid cells after 5 days of culture with erythroid stimulating factors. Factors added to media listed at bottom (n = 3). In all cases, the graph depicts the mean and SD for 3 independent replicates.