Ricerc@Sapienza

Myeloproliferative Neoplasms (MPNs) are distinguished in Polycythemia Vera (PV), Essential Thrombocytemia (ET) and Primary Myelofibrosis (PMF). MPNs are associated to recurrent driver mutations of JAK2, MPL and CALR genes, all causing deregulation of JAK/STAT signaling. Whereas JAK2 and MPL mutations insist directly on JAK/STAT pathway, CALR mutants, associated almost exclusively with ET and PMF, activate the pathway through the interaction with TPO-receptor (MPL). All CALR mutations generate the same common novel peptide, which abolishes the KDEL-ER-retention domain. Such novel peptide mediates the interaction with TPO receptor and arises from a +1 frameshift that converts the first 31 bases of CALR 3'UTR into coding sequence. However, no consideration has been reserved to this 3'UTR region so far. Recently, in two JAK2V617F-negative patients resembling PV, we identified a novel CALR deletion (CALR del24) within such 3'UTR region, not altering the coding sequence. CALR del24 induced properties ascribable to PV in vitro. Importantly, a second CALR deletion of coding sequence, CALR del12, not altering KDEL, was identified in a PV case, but no functional data are yet available about this mutant. Both CALR del24 and del12 are predicted to alter CALR 3'UTR secondary structure and occur in evolutionary conserved regions.
The present project aims to study the role of CALR 3`UTR in normal myelopoiesis and MPNs. We will focus on miRNA regulation and complex regulative functions of 3`UTR, such transcript stability and interactions with proteins. As additional degree of complexity, RNA editing of CALR mRNA will be studied in relationship with 3`UTR functions. All this aspects will be related to the functional characterization of CALR mutants. By exploring these unknown aspects of MPNs in primary samples from normal donors and patients, we propose to shed light on the biology and pathogenesis of these diseases, revealing useful cues for the design of novel targeted treatments.