Transcriptional fine-tuning of microRNA-223 levels directs lineage choice of human hematopoietic progenitors

Abstract

MicroRNAs (miRNAs) regulate cell proliferation, differentiation and death during development and postnatal life. The expression level of mature miRNAs results from complex molecular mechanisms, including the transcriptional regulation of their genes. MiR-223 is a hematopoietic-specific miRNA participating in regulatory signaling networks involving lineage-specific transcription factors (TFs). However, the transcriptional mechanisms governing its expression levels and its functional role in lineage fate decision of human hematopoietic progenitors (HPCs) have not yet been clarified. We found that in CD34þ HPCs undergoing unilineage differentiation/maturation, miR-223 is upregulated more than 10-fold during granulopoiesis, 3-fold during monocytopoiesis and maintained at low levels during erythropoiesis. Chromatin immunoprecipitation and promoter luciferase assays showed that the lineage-specific expression level of mature miR-223 is controlled by the coordinated binding of TFs to their DNA-responsive elements located in 'distal' and 'proximal' regulatory regions of the miR-223 gene, differentially regulating the transcription of two primary transcripts (pri-miRs). All this drives myeloid progenitor maturation into specific lineages. Accordingly, modulation of miR-223 activity in CD34þ HPCs and myeloid cell lines significantly affects their differentiation/ maturation into erythroid, granulocytic and monocytic/macrophagic lineages. MiR-223 overexpression increases granulopoiesis and impairs erythroid and monocytic/macrophagic differentiation. Its knockdown, meanwhile, impairs granulopoiesis and facilitates erythropoiesis and monocytic/macrophagic differentiation. Overall, our data reveal that transcriptional pathways acting on the differential regulation of two pri-miR transcripts results in the fine-tuning of a single mature miRNA expression level, which dictates the lineage fate decision of hematopoietic myeloid progenitors.

MicroRNA-223 dose levels fine tune proliferation and differentiation in human cord blood progenitors and acute myeloid leukemia

“…In line with previously published data [14,25,27], we confirm that miR-223 promotes myeloid/ granulocytic differentiation. We also found in vitro and in vivo evidence that miR-223 increases erythroid and monocytic differentiation.…”

“…The complex miR-223 phenotypes encountered in the different AML mouse models can hardly be reconciled with the published functions of miR-223 in human hematopoiesis, which mainly relate to its role in promoting myeloid differentiation [25,27]. We therefore set out to further define the role of miR-223 in human primary hematopoietic cells.…”

“…Only very recent studies have begun to address its function in primary hematopoietic cells from human cord blood (CB) using in vitro culture and differentiation assays. In vitro experiments suggested that miR-223 positively regulates granulocytic differentiation [14,21,25–27]. It still remains unclear how these findings relate to the phenotype of miR-223 knockout mice, how modulation of miR-223 levels influence steady-state hematopoiesis in humans, and what role this miRNA has in regulating hematopoietic stem- and progenitor-cell function and homeostasis.…”

Function and significance of MicroRNAs in benign and malignant human stem cells

“…In contrast, myeloid balanced hematopoiesis was achieved by overexpression of miR- Notably, a recent study revealed HPCs differentiating into granulocytes and monocytes presented with 10-fold and 3-fold up-regulation of miR-223, respectively. In contrast, HPCs giving rise to erythrocytes maintained low levels of miR-223 (82). Lastly, HSCs undergoing either erythroid or megakaryocytic differentiation were found with upregulated expression of miR-146b (83).…”

MicroRNA-mediated regulation of differentiation and trans-differentiation in stem cells

“…The replacement of NFI-A by C/EBPα and the ensuing granulocytic differentiation are further reinforced by a feedback loop regulation of miR-223, which represses NFI-A. Interestingly, a separate study using CD34 + human hematopoietic progenitor cells (HPCs) showed that the promoter of miR-223 is bound by different transcription factors in a lineage-dependent manner, in which miR-223 is up-regulated during granulopoiesis and monocytic differentiation but remains low during erythropoiesis [89]. Using transfection of synthetic oligonucleotides (mimics and inhibitors), overexpression of miR-223 in CD34 + HPCs promoted granulopoiesis, whereas silencing of it facilitated the erythroid and monocytic pathways.…”