Nuclear factor-erythroid 2 (NF-E2) expression in normal and malignant megakaryocytopoiesis.

Although the transcription factor nuclear factor-erythroid 2 (NF-E2) is known to be functionally linked to the megakaryocytic lineage, little is known about its role in malignant megakaryocytes. We used real-time RT-PCR and Western blotting to investigate expression of NF-E2 and its partner, MafG, in CD34-derived normal (five cases) and malignant megakaryocytes from essential thrombocythemia (ET) patients (eight cases) and in megakaryoblastic cell lines. We also quantitated the mRNA of the thromboxane synthase (TXS) gene, which is directly regulated by NF-E2. Although real-time RT-PCR showed that both a and f NF-E2 isoforms were significantly reduced with respect to the normal counterpart both in ET megakaryocytes and in cell lines (P < or = 0.01), western blotting revealed decreased NF-E2 protein expression only in the latter. However, both the NF-E2a/MafG mRNA ratio (P < or = 0.01) and TXS (P< or = 0.01) mRNA expression were significantly reduced in megakaryocytes from ET patients and cell lines with respect to healthy subjects. These two findings provide strong indirect evidence of altered activity of the a isoform of NF-E2 in malignant megakaryocytes, raising the possibility that NF-E2 could play a role in megakaryocyte transformation.