microRNA-22 promotes megakaryocyte differentiation through repression of its target, GFI1

Abstract

Precise control of microRNA expression contributes to development and the establishment of tissue identity, including in proper hematopoietic commitment and differentiation, whereas aberrant expression of various microRNAs has been implicated in malignant transformation. A small number of microRNAs are upregulated in megakaryocytes, among them is microRNA-22 (miR-22). Dysregulation of miR-22 leads to various hematologic malignancies and disorders, but its role in hematopoiesis is not yet well established. Here we show that upregulation of miR-22 is a critical step in megakaryocyte differentiation. Megakaryocytic differentiation in cell lines is promoted upon overexpression of miR-22, whereas differentiation is disrupted in CRISPR/Cas9-generated miR-22 knockout cell lines, confirming that miR-22 is an essential mediator of this process. RNA-sequencing reveals that miR-22 loss results in downregulation of megakaryocyte-associated genes. Mechanistically, we identify the repressive transcription factor, GFI1, as the direct target of miR-22, and upregulation of GFI1 in the absence of miR-22 inhibits megakaryocyte differentiation. Knocking down aberrant GFI1 expression restores megakaryocytic differentiation in miR-22 knockout cells. Furthermore, we have characterized hematopoiesis in miR-22 knockout animals and confirmed that megakaryocyte differentiation is similarly impaired in vivo and upon ex vivo megakaryocyte differentiation. Consistently, repression of Gfi1 is incomplete in the megakaryocyte lineage in miR-22 knockout mice and Gfi1 is aberrantly expressed upon forced megakaryocyte differentiation in explanted bone marrow from miR-22 knockout animals. This study identifies a positive role for miR-22 in hematopoiesis, specifically in promoting megakaryocyte differentiation through repression of GFI1, a target antagonistic to this process.

Combinatorial effect of miR-486-5p & miR-22-3p mimics thrombopoietin's impact on hematopoietic stem & progenitor cells

“…46,47 Most recently, Weiss and Ito reported that miR-22 is upregulated during in vivo murine megakaryopoiesis, and that miR-22 knockout impairs megakaryocytic differentiation, while miR-22 overexpression promotes megakaryocytic differentiation in the K562 cell line. 48 Their results suggest a similar miR-22 role as we report here ( Figure 2D). miR-22-3p was also most recently shown to regulate mTOR signaling by targeting eukaryotic translation initiation factor 4E-binding proteins (eIF4EBP3) in human cervical squamous carcinoma cells.…”

“…47 The latter is consistent with the finding that miR-22 promotes megakaryopoiesis by repressing the repressive transcription factor GFI1. 48 The proposed model of Figure 7 captures and integrates our data and the current knowledge. This project was supported by a grant (CBET-1804741) by the US National Science Foundation.…”

MicroRNAs in Platelets: Should I Stay or Should I Go?

“…As we have seen, there is evidence of the possible regulation of megakaryopoiesis by miRNAs, a connection between TF and miRNAs, and that the expression of the miRNA-coding genes is affected [41]. We do not know if this is due to a causal relationship or a consequence of the maturation process, perhaps [53] In this case, miR-22 may regulate GFI1B indirectly through GFI1 because GFI1 and GFI1B could compete for DNA occupancy [53] both, but what we do know is that it can have a side effect on the expression of many other genes.…”

Post-Transcriptional Expression Control in Platelet Biogenesis and Function

“…Additionally, miR-130 targets the MAF BZIP Transcription Factor B ( MAFB ), which increases with terminal MK differentiation and induces activation of the Integrin Alpha 2b ( ITGA2B ) gene [ 127 ]. Very recently, miR-22 has been shown to promote megakaryocyte differentiation through repression of its target Growth Factor Independent 1 Transcriptional Repressor ( GFI1 ) [ 128 ]. Ex vivo, megakaryocyte differentiation from hematopoietic stem/progenitor cells (HSPCs) and generation of platelets was also shown to be regulated by miRNAs.…”