MOLECULAR ANALYSIS OF THE ERYTHROPOIETIN RECEPTOR SYSTEM IN PATIENTS WITH POLYCYTHEMIA-VERA

Erythropoietin (EPO) is a potent regulator of the viability, prolifera tion and differentiation of erythroid progenitor cells. Its effect is mediated by binding to the erythropoietin receptor (EPO-R), a member o f a new cytokine receptor family. Alterations of the EPO/EPO-R system have recently been shown to be involved in the pathogenesis of familia l erythrocytosis and polycythaemia vera (PV). In order to define wheth er genetic changes in the EPO-R gene and its ligand play a role in the development of PV, the structure and expression levels of the EPO-R a nd EPO genes were examined in samples from bone marrow and/or peripher al blood mononuclear cells of 24 patients with PV. As expected, EPO se rum levels were low and no detectable level of EPO mRNA was found by r everse polymerase chain reaction (RT-PCR) in the peripheral blood mono nuclear cells of our PV patients. To search for structural alterations of the EPO-R, cDNA samples were subjected to PCR and SSCP analysis as well as sequencing. Heterogenous expression of EPO-R mRNA was observe d without any structural changes, as revealed by RT-SSCP analysis usin g overlapping primers spanning the whole coding region of the EPO-R ge ne. Structural integrity of the EPO-R was further confirmed by sequenc ing of cloned PCR products. These data suggest that the mechanisms for the development of PV do not involve structural changes of the EPO-R gene.