Downregulation of KLF4 activates embryonic and fetal globin mRNA expression in human erythroid progenitor cells.

The Kruppel-like factor (KLF) family dominates highly conserved three zinc finger DNA binding domains at the C-terminus and variable transactivation domains at the N-terminus. Humans possess 18 KLF genes that are differentially expressed in various tissues. Several KLFs recognize a specific CACCC DNA motif that is commonly found within hematopoietic-specific promoters. To investigate those KLFs that are involved in human hemoglobin (Hb) switching, the present study analyzed a previous microarray data set from fetal and adult erythroid cells and validated the mRNA expression levels of 18 KLFs by reverse transcription-quantitative PCR (RT-qPCR). KLF with a decreased expression level in the fetuses was selected for a functional study in human erythroid progenitor cells using lentiviral-based short hairpin RNA knockdown. The fetuses demonstrated a lower level of KLF4 mRNA expression when compared with the adults. Downregulation of KLF4 in erythroid progenitor cells from healthy individuals and individuals with β0-thalassemia/HbE evidenced the increasing embryonic and fetal globin mRNA expression with neither significant cytotoxicity nor gene expression alteration of the examined globin regulators, KLF1, B-cell lymphoma/leukemia 11A and lymphoma/leukemia-related factor. These findings demonstrate that the downregulation of KLF4 is associated with increased embryonic and fetal globin gene expression in human erythroid progenitor cells. Moreover, identifying putative compounds or molecular approaches that effectively downregulate KLF4 and further induce embryonic globin expression may provide an alternative therapeutic strategy for α-globin substitution in severe α-thalassemia.