Regulatory mRNA/microRNA networks in CD34+ cells from Primary Myelofibrosis

Primary myelofibrosis (PMF) is a clonal disorder of a hematopoietic stem cell included in the Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs), together with polycythemia vera and essential thrombocythemia. The molecular mechanisms of these diseases were partially unravelled in 2005 with the identification of somatic gain-of-function of Janus kinase 2 (JAK2) and Thrombopoietin Receptor (MPL), after which many other mutated genes were found. Moreover, aberrant microRNA (miRNA) expression seems to add up to the molecular complexity of MPNs, as specific miRNA signatures discriminates MPN cells from those of normal donors. In order to have a comprehensive picture of miRNA deregulation and its relationship with differential gene expression in PMF cells, we obtained mRNA and miRNA profiles in the same CD34+ cells from 31 healthy donors and 42 PMF patients by means of Affymetrix technology. Several miRNAs involved in hematological malignancies or known as oncomirs resulted upregulated in PMF samples (hsa-miR-155-5p, miRNAs belonging to the miR-17-92 cluster), whereas other aberrantly expressed miRNAs have never been described in the hematological context (hsa-miR-335). Next, we carried out an in silico integrative analysis (IA) with Ingenuity Pathway Analysis software, which combines the computational predicted targets with the gene expression data to construct regulatory networks of the functional miRNA-mRNA interactions. Of note, IA identified a network potentially involved in PMF pathogenesis, in which the upregulated oncomirs miR-155-5p and miR29a-3p could explain the downregulation of targets whose lower expression was already described in myeloproliferative phenotypes (NR4A3, CDC42, HMGB3), and of the chromatin remodeler JARID2, which is frequently deleted in leukemic transformation of MPNs. Finally, we demonstrated the JARID2 downregulation in CD34+ cells plays a role in the abnormal megakaryopoiesis, and contributes to PMF pathogenesis.