ZNF802 (JAZF1), a Possible New Therapeutic Target for Treatment of β-Thalassemia

β-Thalassemias are groups of inherited blood disorders caused by reduced or absent production of β-globin chains of adult hemoglobin (HbA; α2β2). The severely affected patients with β-thalassemia require lifelong blood transfusion and chelation therapy. Reactivation of fetal hemoglobin (HbF; α2γ2) could ameliorate the symptoms of patients via increased total hemoglobin production and reduced imbalanced α- to non-α-globin synthesis. Hemoglobin switching during human development requires activities of several transcription factor proteins, including those bind to the globin gene promoters. However, the regulation of fetal to adult hemoglobin switching is not fully understood. Previously, we have carried out the microarray analysis comparing human erythroblasts derived from therapeutic aborted fetal liver and adult peripheral blood. The results showed that ZNF802 mRNA is among the transcripts that up-regulated in adult erythroblast of greater than 2-fold change. ZNF802, also called JAZF1, is a 27 kDa protein containing two zinc finger motifs that acting as transcriptional repressor by binding to the direct repeat (DR) elements on DNA. In this study, quantitative RT-PCR was performed in order to validate the microarray data. We observed 13-fold up-regulation of ZNF802 in adult erythroid cells compared to those cells derived from fetal liver. To further elucidate the role of ZNF802 in reduction of HbF expression in adult erythroids, the lentivirus carrying ZNF802 specific shRNA and non-targeted shRNA were designed and constructed for transduction in erythroblasts. Hematopoietic CD34⁺ progenitor cells were isolated from β-thalassemia/HbE patients (n=9) and subjected to ex vivo two-phase liquid erythroid culture. The results showed the reduction of greater than 90% of ZNF802 transcript and nearly undetectable level of ZNF802 protein in cells transduced with the ZNF802 shRNA lentivirus. As expected, the level of γ-globin transcript and levels of HbF were increased in ZNF802 knockdown erythroid cells in β-thalassemia/HbE (5-fold changed and HbF 26.9±7.4% vs 18.5±6.8% in non-targeted shRNA (p-value = 0.04), respectively). Interestingly, we found up-regulation of the embryonic ε-globin and ζ-globin transcripts in knockdown ZNF802 cells compared to non-targeted shRNA control (15-fold and 10-fold changed (p-value = 0.01), respectively). To note, the diminishing of ZNF802 effect on the proliferation and differentiation pattern of erythriod cells was not found. Altogether, our findings suggested that ZNF802 may play a role as the transcriptional repressor of γ-globin gene in human adult erythroid cells, thus served as a possible new therapeutic target for treatment of β-thalassemia. The molecular mechanisms underlying the ZNF802 mediated HbF reduction are underway.