MicroRNA fingerprints during human megakaryocytopoiesis

Abstract

microRNAs are a highly conserved class of noncoding RNAs with important regulatory functions in proliferation, apoptosis, development, and differentiation. To discover novel regulatory pathways during megakaryocytic differentiation, we performed microRNA expression profiling of in vitro-differentiated megakaryocytes derived from CD34 ؉ hematopoietic progenitors. The main finding was down-regulation of miR-10a, miR-126, miR-106, miR-10b, miR-17 and miR-20. Hypothetically, the down-regulation of microRNAs unblocks target genes involved in differentiation. We confirmed in vitro and in vivo that miR-130a targets the transcription factor MAFB, which is involved in the activation of the GPIIB promoter, a key protein for platelet physiology. In addition, we found that miR-10a expression in differentiated megakaryocytes is inverse to that of HOXA1, and we showed that HOXA1 is a direct target of miR-10a. Finally, we compared the microRNA expression of megakaryoblastic leukemic cell lines with that of in vitro differentiated megakaryocytes and CD34 ؉ progenitors. This analysis revealed up-regulation of miR-101, miR-126, miR-99a, miR-135, and miR-20. Our data delineate the expression of microRNAs during megakaryocytopoiesis and suggest a regulatory role of microRNAs in this process by targeting megakaryocytic transcription factors.leukemia ͉ hematopoiesis

Genomics and transcriptomics of megakaryocytes and platelets: Implications for health and disease

“…Over the last decade this traditional model of MEP to megakaryocyte and/or erythroblast has been challenged by new findings that suggest that there is a subset of HSCs that express von Willebrand factor (VWF), have a strong megakaryocyte bias and limited lymphoid potential 27. More importantly, the VWF expressing HSCs can give rise to HSCs that do not express VWF while the opposite is not true, indicating that these cells are high in the hematopoietic hierarchy 20, 28. Both of these models may not be mutually exclusive with megakaryocyte differentiation occurring through both the classic MEP pathway and by way of HSCs that exhibit an early megakaryocyte commitment in response to stress (ie, inflammation, chemotherapy, etc.)…”

“…Aberrant miRNA expression has been associated with a number of hematologic diseases, including leukemia, lymphoma, and myeloproliferative disorders. The miRNA signature of megakaryocytes derived from human CD34+ HSCs has been described suggesting that these miRNAs release the repression of target megakaryocytic transcription factors 28. De‐repression of these target genes theoretically allows the precursor cells to proceed in their differentiation program toward the megakaryocyte lineage.…”

Megakaryocytic expression of miRNA 10a, 17-5p, 20a and 126 in Philadelphia chromosome-negative myeloproliferative neoplasm

“…During differentiation of non-leukaemic CD34 + cells towards a megakaryocytic phenotype several miRNA, including miRNA 126 (localised on chromosome region 9q34), members of the miRNA 17-5p-92 cluster (miRNA 17-5p and 20a, both 13q31) and particularly miRNA 10a (17q21), were down-regulated [11]. Investigation of potential miRNA targets, such as homeobox gene (HOX) transcription factors, which are involved in embryogenesis, haematopoiesis and myeloid leukaemogenesis [12], revealed an up-regulation of HOXA1 mRNA and protein during in vitro megakaryopoiesis, which was reciprocal to miRNA 10a down-regulation and vice versa miRNA 10a over-expression in MEG01 and K562 cell lines reduced HOXA1 expression [11].…”

“…Investigation of potential miRNA targets, such as homeobox gene (HOX) transcription factors, which are involved in embryogenesis, haematopoiesis and myeloid leukaemogenesis [12], revealed an up-regulation of HOXA1 mRNA and protein during in vitro megakaryopoiesis, which was reciprocal to miRNA 10a down-regulation and vice versa miRNA 10a over-expression in MEG01 and K562 cell lines reduced HOXA1 expression [11]. A potential target of the miRNA 17-5p-92 cluster and miRNA 126 is the Runt-related transcription factor 1 (RUNX1, also designated acute myeloid leukemia 1, AML1) [11] which is one of the central transcription factors in normal and leukaemic megakaryopoiesis [13,14]. In monocytic differentiation, it has been shown that RUNX1 is inhibited by the miRNA 17-5p-92 cluster and in a negative feed-back regulation mechanism RUNX1 protein binds to the promoter of miRNA 17-5p-92 cluster genes [15].…”

“…Based on these in vitro-derived results on non-neoplastic megakaryocytic differentiation [11], we performed an in situ analysis of laser-microdissected bone marrow megakaryocytes from Ph − MPN patients in order to clarify whether the aberrant morphological differentiation is associated to aberrant expression of miRNA 10a, 126, 17-5p and 20a and their potential targets HOXA1 and RUNX1.…”