Impaired DNA damage response and inflammatory signalling underpins hematopoietic stem cell defects inGata2haploinsufficiency

Abstract

ClinicalGATA2deficiency syndromes arise from germline haploinsufficiency inducing mutations inGATA2, resulting in immunodeficiency that evolves to myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML). HowGATA2haploinsufficiency disrupts the function and transcriptional network of hematopoietic stem/progenitors (HSCs/HSPCs) to facilitate the shift from immunodeficiency to pre-leukemia is poorly characterised. Using a conditional mouse model harboring a single allele deletion ofGata2from the start of HSC developmentin utero, we identified pervasive defects in HSPC differentiation from young adultGata2haploinsufficient mice during B-cell development, early erythroid specification, megakaryocyte maturation to platelets and inflammatory cell generation.Gata2haploinsufficiency abolished HSC self-renewal and multi-lineage differentiation capacity. These functional alterations closely associated with deregulated DNA damage responses and inflammatory signalling conveyed fromGata2haploinsufficient HSCs. We identified genetic interplay betweenGata2andAsxl1, a driver of DNA damage and inflammation and, notably, a recurrent secondary mutation found inGATA2haploinsufficiency disease progression to MDS/AML. shRNA mediated knockdown ofAsxl1inGata2haploinsufficient HSPCs led to an enhanced differentiation blockin vitro. By analysis of HSCs from young adult compoundGata2/Asxl1haploinsufficient mice, we discovered hyperproliferation of double haploinsufficient HSCs, which were also functionally compromised in transplantation compared to their singleGata2 or Asxl1haploinsufficient counterparts. Through bothGata2/Asxl1dependent and unique transcriptional programs, HSCs from compoundGata2/Asxl1haploinsufficient fortified deregulated DNA damage responses and inflammatory signalling initiated inGata2haploinsufficient HSCs and established a broad pre-leukemic program. Our data reveal howGata2haploinsufficiency initially drives deregulation of HSC genome integrity and suggest the mechanisms of how secondary mutations likeASXL1take advantage of HSC genomic instability to nurture a pre-leukemic state inGATA2haploinsufficiency syndromes.