Reciprocal Regulation Of Gamma-Globin Expression By Exo-Mirnas: Relevance To Gamma-Globin Silencing In Beta-Thalassemia Major

Induction of fetal hemoglobin (HbF) is a promising strategy in the treatment of beta-thalassemia major (beta-TM). The present study shows that plasma exosomal miRNAs (exo-miRs) are involved in gamma-globin regulation. Exosomes shuttle miRNAs and mediate cell-cell communication. MiRNAs are regulators of biological processes through post-transcriptional targeting. Compared to HD (Healthy Donor), beta-TM patients showed increased levels of plasma exosomes and the majority of exosomes had cellular origin from CD34+cells. Further, HD and beta-TM exosomes showed differential miRNA expressions. Among them, deregulated miR-223-3p and miR-138-5p in beta-TM exosomes and HD had specific targets for.-globin regulator and repressor respectively. Functional studies in K562 cells showed that HD exosomes and miR-138-5p regulated gamma-globin expression by targeting BCL11A. beta-TM exosomes and miR-223-3p down regulated gamma-globin expression through LMO2 targeting. Importantly, miR-223-3p targeting through sponge repression resulted in gamma-globin activation. Further, hnRNPA1 bound to stem-loop structure of pre-miR-223 and we found that hnRNPA1 knockdown or mutagenesis at miR-223-3p stem-loop sequence resulted in less mature exo-miR-223-3p levels. Altogether, the study shows for the first time on the important clinical evidence that differentially expressed exo-miRNAs reciprocally control gamma-globin expressions. Further, the hnRNPA1-exo-miR-223-LMO2 axis may be critical to gamma-globin silencing in beta-TM.