A critical role of RUNX1 in governing megakaryocyte-primed hematopoietic stem cell differentiation

Abstract

As a member of the RUNT domain family core-binding transcription factors, RUNX1 is crucial for multiple stages of hematopoiesis and its mutation can cause familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML). Previous work has established that RUNX1 is involved in the maturation of megakaryocytes and the production of platelets. Recently studies have shown that there exists a subpopulation of hematopoietic stem cells (HSCs) with relatively high expression of vWF and CD41 at the apex of the HSC hierarchy, termed MK-HSCs, which can give rise to megakaryocytes without going through the traditional differentiation trajectory from HSC via MPP and MEP. Here, by using Runx1F/FMx1-Cre mouse model we discovered that the MK-HSC to megakaryocyte direct differentiation can happen within one cell division and RUNX1 is an important regulator in the process. Runx1 knockout results in a drastic decrease in platelet counts and a severe defect in the differentiation from MK-HSCs to megakaryocytes. Single cell RNA sequencing (RNAseq) analysis shows that MK-HSCs have a distinct gene expression signature compared with non-MK-HSCs, and Runx1 deletion alters the platelet and megakaryocyte related gene expression in MK-HSCs. Further bulk RNAseq and Cut & Run analyses show that RUNX1 binds to multiple essential megakaryocyte/platelet developmental genes such as Spi1, Selp and Itga2b and regulates their expressions in MK-HSCs. Thus, by modulating the expression of megakaryocyte-related genes, RUNX1 governs the direct differentiation of MK-HSCs to megakaryocytes and platelets.

Enigmatic missense mutations can cause disease via creation ofde novonuclear export signals

“…Finally, we observe in humanized Etv6 S211I P216L/WT mice depletion of HSCs with high expression of c-Kit, a population previously described to have a megakaryocyte lineage bias 35 , with megakaryocytes arising directly from such HSCs 45 . This raises the possibility that the megakaryocyte progenitor defect and thrombocytopenia associated with ETV6 mutations arise directly from a defect in HSCs, which would mirror a similar mechanism described for RUNX1 mutation-associated thrombocytopenia 46 .…”

RUNX1 C-terminal mutations impair blood cell differentiation by perturbing specific enhancer-promoter networks

“…These pathways relate to the known role of RUNX1 in hematopoietic disease as well as MK differentiation and function. 27 , 29 , 36 , 37 , 38 We also performed gene set enrichment analysis (GSEA) 39 and revealed negative enrichment of RUNX1-regulated megakaryocytic and hematopoietic stem cell (HSC) differentiation gene sets in RUNX1 R320∗ cells ( Figure 3 E). We identified specific hematopoietic genes that were dysregulated in RUNX1 R320∗ cells using Reactome and gene ontology (GO) databases ( supplemental Figure 2 B).…”

Acute myeloid leukemia with mixed phenotype is characterized by stemness transcriptomic signatures and limited lineage plasticity

“…58 RUNX1 has been shown to play an important role in lineage specification in hematopoietic and nonhematopoietic system. [59][60][61][62][63][64][65] RUNX1 mutations lead to megakaryocytic differentiation block but increased plasmacytoid dendritic cell differentiation. 65,66 As RUNX1 largely functions as a suppressor, loss-of-function mutations may result in imbalance of lineage specific (i.e.…”

“…[59][60][61][62][63][64][65] RUNX1 mutations lead to megakaryocytic differentiation block but increased plasmacytoid dendritic cell differentiation. 65,66 As RUNX1 largely functions as a suppressor, loss-of-function mutations may result in imbalance of lineage specific (i.e. lymphoid) gene expression.…”