miR-494-3p overexpression promotes megakaryocytopoiesis in primary myelofibrosis hematopoietic stem/progenitor cells by targeting SOCS6

// Sebastiano Rontauroli 1, * , Ruggiero Norfo 1, * , Valentina Pennucci 1 , Roberta Zini 1 , Samantha Ruberti 1 , Elisa Bianchi 1 , Simona Salati 1 , Zelia Prudente 1 , Chiara Rossi 1 , Vittorio Rosti 2 , Paola Guglielmelli 3 , Giovanni Barosi 2 , Alessandro Vannucchi 3 , Enrico Tagliafico 4 , Rossella Manfredini 1 1 Centre for Regenerative Medicine, Life Sciences Department, University of Modena and Reggio Emilia, Modena, Italy 2 Center for The Study of Myelofibrosis, Biotechnology Research Area, IRCCS Policlinico S. Matteo Foundation, Pavia, Italy 3 CRIMM-Center for Research and Innovation for Myeloproliferative Neoplasms, AOU Careggi, and Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy 4 Center for Genome Research, University of Modena and Reggio Emilia, Modena, Italy * These authors have contributed equally to this work Correspondence to: Rossella Manfredini, email: rossella.manfredini@unimore.it Keywords: miR-494-3p, SOCS6, primary myelofibrosis, megakaryocytopoiesis, CD34+ cells Received: August 16, 2016     Accepted: January 23, 2017     Published: February 09, 2017 ABSTRACT Primary myelofibrosis (PMF) is a chronic Philadelphia-negative myeloproliferative neoplasm characterized by hematopoietic stem cell-derived clonal myeloproliferation, involving especially the megakaryocyte lineage. To better characterize how the altered expression of microRNAs might contribute to PMF pathogenesis, we have previously performed the integrative analysis of gene and microRNA expression profiles of PMF hematopoietic stem/progenitor cells (HSPCs), which allowed us to identify miR-494-3p as the upregulated microRNA predicted to target the highest number of downregulated mRNAs. To elucidate the role of miR-494-3p in hematopoietic differentiation, in the present study we demonstrated that miR-494-3p enforced expression in normal HSPCs promotes megakaryocytopoiesis. Gene expression profiling upon miR-494-3p overexpression allowed the identification of genes commonly downregulated both after microRNA overexpression and in PMF CD34+ cells. Among them, suppressor of cytokine signaling 6 (SOCS6) was confirmed to be a miR-494-3p target by luciferase assay. Western blot analysis showed reduced level of SOCS6 protein as well as STAT3 activation in miR-494-3p overexpressing cells. Furthermore, transient inhibition of SOCS6 expression in HSPCs demonstrated that SOCS6 silencing stimulates megakaryocytopoiesis, mimicking the phenotypic effects observed upon miR-494-3p overexpression. Finally, to disclose the contribution of miR-494-3p upregulation to PMF pathogenesis, we performed inhibition experiments in PMF HSPCs, which showed that miR-494-3p silencing led to SOCS6 upregulation and impaired megakaryocyte differentiation. Taken together, our results describe for the first time the role of miR-494-3p during normal HSPC differentiation and suggest that its increased expression, and the subsequent downregulation of its target SOCS6, might contribute to the megakaryocyte hyperplasia commonly observed in PMF patients.