Modulation of miR 185 5p expression by EBV miR BART6 contributes to developmental differences in ABCG4 gene expression in human megakaryocytes.
Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by low platelet count and bleeding, and is usually triggered by viral infections. We previously reported that 14 viral microRNAs of megakaryocytes cultured with serum from patients with ITP, including ebv miR BART6, are up regulated. Previous research has reported that ebv miR BART6 down regulated the expression of miR 185 5p. We therefore predicted that the ABCG4 gene, which is highly expressed in megakaryocyte progenitor cells, is a direct target of miR 185 5p. We hypothesized that ebv miR BART6 may play a role in development and differentiation of megakaryocytes. First, we verified the negative regulation of ABCG4 by miR 185 5p through luciferase assay analysis. Second, after transfection of ebv miR BART6 into megakaryocytes developing from normal cord blood mononuclear cells (MNCs) we found that the level of miR 185 5p in the ebv miR BART6 group was reduced to almost a third of that in the control groups, accompanied by up regulation of ABCG4 at both the mRNA and protein levels. Meanwhile, proliferation of megakaryocytes was significantly repressed in the ebv miR BART6 group compared with the blank and negative control groups (14.89% 3.13% 34.15% 2.42% and 30.96% 4.37% respectively; P<0.001) Our results further revealed that ebv miR BART6 inhibited megakaryocyte colony unit formation, decreased CD41 expression and inhibited megakaryocyte polyploidization. These data suggest a new paradigm to explain the mechanisms underlying ITP, involving the regulation of megakaryocytopoiesis by viral microRNAs through the intronic hsa microRNA.
The international journal of biochemistry cell biology