RED CELLS A sustained and pancellular reversal of gamma-globin gene silencing in adult human erythroid precursor cells

We systematically compared cytokinemediated increasesordecreases inproliferation with globin gene and protein expression in adult human erythroblasts. Despite their opposite effects on growth, stem cell factor (SCF) and transforming growth factorbeta (TGF-B) had synergistic effects with respect to fetal hemoglobin (HbF): average HbF/HbF adult hemoglobin (HbA) ratio in erythropoietin (EPO) 1.4 1.0%; EPO TGF-B 10.8 1.9%; EPO SCF 19.1 6.2%; and EPO SCF TGF-B (EST) 39.3 6.3%. Polymerase chain reaction (PCR) revealed significant increases in gamma-globin transcripts that were balanced by reduced betaglobin transcripts. Single-cell quantitative PCR demonstrated a complete reversal of gamma-globin gene silencing with detectable gamma-globin mRNA in more than 95% of the cells. Immunostaining with HbF antibodies also showed a pancellular distribution in EST (96.2 0.01% HbF positive) compared with a heterocellular distribution in EPO (42.9 0.01% HbF positive). As shown here for the first time, a robust and pancellular reversal of gamma-globin gene silencing among hemoglobinized erythroblasts from adult humans may be achieved in the absence of hereditary mutation or direct genomic manipulation. (Blood. 2005;105:387-393)