LRF/ZBTB7A is a transcription factor that has been recently identified as a new key regulator of fetal hemoglobin (HbF; α2γ2) production in erythroid cells. Reduction of LRF/ZBTB7A expression led to increases in levels of HbF in human CD34+ hematopoietic stem and progenitor cell (HSPC)-derived erythroblast and in human immortalized erythroid line (HUDEP-2). Since reactivation of γ-globin gene is associated with the improvement of clinical manifestations of β-hemoglobinopathy patients, decrement in LRF/ZBTB7A expression might be a substantial interest as a novel target for gene therapy in β-thalassemia. In this study, we investigated the effects of LRF/ZBTB7A downregulation in erythroid cells derived from β-thalassemia/HbE patients in order to evaluate its therapeutic potential. The hematopoietic CD34+ progenitor cells were collected from 3 patients and 3 healthy normal individuals' peripheral blood and subjected for in vitro erythroblast culture. The cells were transduced with lentivirus carrying LRF/ZBTB7A specific shRNA, and used untransduced cells and non-targeted control shRNA (shNTC) as experimental controls. The LRF/ZBTB7A shRNA reduced LRF/ZBTB7A transcript and protein to nearly undetectable levels. Interestingly, downregulation of LRF/ZBTB7A increased expression of γ-globin, ε-globin and ζ-globin in both adult normal and β-thalassemia/HbE derived cells, whereas α-globin, β-globin and δ-globin expression were decreased. As previously reported, we found that the LRF/ZBTB7A knockdown produced a robust increase in HbF levels in both normal (43.3±9.0% vs. 5.9±2.1% in shNTC) and β-thalassemia/HbE erythroblasts (78.1±3.5% vs. 26.3±3.9% in shNTC). Noteworthy, the delay of erythroid differentiation was observed in the LRF/ZBTB7A knockdown cells of both derived from β-thalassemia/HbE patients and normal control, suggesting an additional role of LRF/ZBTB7A in regulating erythroid maturation. These data support the manipulation of LRF/ZBTB7A as one of the most interesting gene therapy candidates for treating the β-thalassemia, but the effect on erythroid cell maturation is needed to be concerned and required further investigation. Disclosures No relevant conflicts of interest to declare.

Defective hemoglobin production and ineffective erythropoiesis contribute to the pathophysiology of thalassemia syndromes. Previous studies in the field of erythropoiesis mainly focused on the severe forms of thalassemia, such as β-thalassemia major, while mechanisms underlying the pathogenesis of other thalassemia syndromes remain largely unexplored. The current study aimed to investigate the intrinsic pathophysiological properties of erythroid cells derived from the most common forms of thalassemia diseases, including α-thalassemia (hemoglobin H and hemoglobin H-Constant Spring diseases) and β-thalassemia (homozygous β0-thalassemia and β0-thalassemia/hemoglobin E diseases), under an identical in vitro erythroid culture system. Cell proliferation capacity, differentiation velocity, cell death, as well as globin synthesis and the expression levels of erythropoiesis modifying factors were determined. Accelerated expansion was found in erythroblast cells derived from all types of thalassemia, with the highest degree in β0-thalassemia/hemoglobin E. Likewise, all types of thalassemia showed limited erythroid cell differentiation, but each of them manifested varying degrees of erythroid maturation arrest corresponding with the clinical severity. Robust induction of HSP70 transcripts, an erythroid maturation-related factor, was found in both α- and β-thalassemia erythroid cells. Increased cell death was distinctly present only in homozygous β0-thalassemia erythroblasts and associated with the up-regulation of pro-apoptotic (Caspase 9, BAD, and MTCH1) genes and down-regulation of the anti-apoptotic BCL-XL gene.

Reactivating of fetal hemoglobin (HbF; α2γ2) can ameliorate the severity of β-thalassemia disease by compensating for adult hemoglobin deficiency in patients. Previously, microarray analysis revealed that zinc finger protein (ZNF)802 (also known as Juxta-posed with another zinc finger gene-1 (JAZF1)) was upregulated in human erythroblasts derived from adult peripheral blood compared with fetal liver-derived cells, implying a potential role as a HbF repressor. However, deficiency in ZNF802 induced by lentiviral shRNA in β0-thalassemia/hemoglobinE erythroblasts had no effect on erythroblast proliferation and differentiation. Remarkably, the induction of HBG expression was observed at the transcriptional and translational levels resulting in an increase of HbF to 35.0 ± 3.5%. Interestingly, the embryonic globin transcripts were also upregulated but the translation of embryonic globin was not detected. These results suggest ZNF802 might be a transcriptional repressor of the γ-globin gene in adult erythroid cells.