Project description:The GATA2 transcription factor is a pivotal regulator of hematopoiesis. Disruptions in the GATA2 gene drive severe hematologic abnormalities and are associated with an increased risk of myelodysplastic syndromes and acute myeloid leukemia; however, the mechanisms underlying the pathophysiology of GATA2 deficiency remain still unclear. We developed two different mouse models that are based on serial and limiting donor cell transplantation of (aged) GATA2 haploinsufficient cells and mirror the symptoms of GATA2 deficiency. Similar to what has been observed in patients, our models show that GATA2 haploinsufficiency leads to B lymphopenia, monocytopenia, lethal bone marrow failure (BMF), myelodysplasia and lymphoblastic leukemia. Leukemia arises exclusively as a result of BMF, driven by somatic aberrations and accompanied by increased Myc target expression and genomic instability. These findings were confirmed in human GATA2+/- K562 cell lines showing defects in cytokinesis and are in line with the fact that monosomy 7 and trisomy 8 are frequent events in patients with MDS.
Project description:GATA2 deficiency is an autosomal dominant germline disorder of immune dysfunction and bone marrow failure with a high propensity for leukemic transformation in adolescents, present in up to 7% of pediatric myelodysplastic syndrome (MDS) and 15% of advanced MDS cases. While sequencing studies have identified several secondary mutations thought to contribute to malignancy, the mechanisms of disease progression have been difficult to identify due to a lack of disease-specific experimental models. Here, we generated a murine model of one of the most common GATA2 mutations associated with leukemic progression in GATA2 deficiency, Gata2R396Q/+. While mutant mice exhibit mild defects in peripheral blood output throughout life, they display significant hematopoietic abnormalities in the bone marrow (BM), including a reduction in hematopoietic stem cell (HSC) function and intrinsic biases toward specific stem cell subsets that differ from previous models of GATA2 loss. Supporting this observation, single-cell RNA sequencing of BM hematopoietic progenitors revealed a loss of HSC stemness, myeloid-bias, and accelerated ageing phenotype. Importantly, we show that Gata2R396Q/+ exerts effects early in hematopoietic development, as mutant mice generate fewer HSCs in the aorta gonad mesonephros, and fetal liver HSCs have reduced function. This reduced pool of HSCs and aged phenotype could be potential contributors to leukemic transformation in patients, and our model provides a useful tool to study the mechanisms of malignant transformation in GATA2 deficiency.
Project description:The Gata2 transcription factor is a pivotal regulator of hematopoietic stem cell (HSC) development and maintenance. Gata2 functions in the embryo during endothelial cell to hematopoietic cell transition (EHT) to affect hematopoietic cluster, HPC and HSC formation. Although previous studies of cell populations phenotypically enriched in HPCs and HSCs show expression of Gata2, there has been no direct study of Gata2 expressing cells during normal hematopoiesis. In this study we generate a Gata2 Venus reporter mouse model with unperturbed Gata2 expression to examine the hematopoietic function and transcriptome of Gata2 expressing and nonexpressing cells. Gata2Venus- HPCs 1 replicate, Gata2Venus+ HPCs 1 replicate
Project description:We generated homozygous GATA2 knockout human embryonic stem cells (GATA2-/- hESCs) and analyzed their blood differentiation potential. Paritcularly at the hemogenic endothelium (HE) stage and hematopoietic progenitor cell (HPC) stage. Our result revealed that GATA2-/- hESCs displayed attenuated generation of CD34+CD43+ HPCs, due to the impairment of endothelial to hematopoietic transition (EHT). However, GATA2-/- hESCs retained the potential to generate erythroblasts, macrophages, but never granulocytes. Through RNA-Seq and further rescue experiment, we further identified that SPI1 was responsible for the defect of GATA2-/- hESCs in generation of CD34+CD43+ HPCs and granulocytes.
Project description:The Gata2 transcription factor is a pivotal regulator of hematopoietic stem cell (HSC) development and maintenance. Gata2 functions in the embryo during endothelial cell to hematopoietic cell transition (EHT) to affect hematopoietic cluster, HPC and HSC formation. Although previous studies of cell populations phenotypically enriched in HPCs and HSCs show expression of Gata2, there has been no direct study of Gata2 expressing cells during normal hematopoiesis. In this study we generate a Gata2 Venus reporter mouse model with unperturbed Gata2 expression to examine the hematopoietic function and transcriptome of Gata2 expressing and nonexpressing cells.
Project description:Patients with GATA2 deficiency are predisposed to developing myelodysplastic syndrome (MDS), which can progress to acute myeloid leukemia (AML). This progression is often associated with the acquisition of additional cytogenetic and somatic alterations. Mutations in SETBP1 and ASXL1 genes are recurrently observed in GATA2 patients, but their precise roles in disease progression remain poorly understood. Here we developed a hiPSC-based system to investigate the functional impact of SETBP1 and ASXL1 mutations in the context of germline GATA2 haploinsufficiency. Using precise genome editing, we recreated patient-relevant combinations of these mutations to model distinct premalignant stages of GATA2 deficiency. We demonstrate that heterozygous GATA2 mutation alone has a limited impact on early hematopoietic progenitors, without disrupting myeloid differentiation. In contrast, acquisition of SETBP1 or ASXL1 mutations impairs hematopoietic differentiation in a GATA2 deficient background, leading to a premalignant state marked by reduced myeloid progenitor output. Strikingly, the combination of all three mutations results in a severe depletion of myeloid progenitors, closely recapitulating hematopoietic defects observed in GATA2-related MDS and highlighting a synergistic interplay among the mutations. We provide new insights into the molecular mechanism underlying GATA2 deficiency progression, revealing that SETBP1 mutation plays a dominant role in establishing a stable chromatin accessibility landscape, even when co-occurring with ASXL1. Our study establishes a novel humanized model system for studying GATA2 deficiency. This model provides new insights into the cellular and molecular events underlying the progression of myeloid impairment in GATA2 deficiency and represents a platform for testing future therapeutic strategies.
Project description:Cell fate is established through coordinated gene expression programs in individual cells. Regulatory networks that include the Gata2 transcription factor play central roles in hematopoietic fate establishment. Whereas Gata2 is essential to the embryonic development and function of hematopoietic stem cells that form the adult hierarchy, little is known of the in vivo expression dynamics of Gata2 in single cells. Here we examine Gata2 expression in single aortic cells as they establish hematopoietic fate in Gata2Venus mouse embryos. Time-lapse imaging reveals rapid pulsatile level changes in Gata2 reporter expression in cells undergoing endothelial-to-hematopoietic-transition. Moreover, Gata2 reporter pulsatile expression is dramatically altered in Gata2+/- aortic cells, which undergo fewer transitions and are reduced in hematopoietic potential. Our novel finding of dynamic pulsatile expression of Gata2 suggests a highly unstable genetic state in single cells concomitant with their transition to hematopoietic fate. This reinforces the notion that threshold levels of Gata2 influence fate establishment and has implications for transcription factor-related hematologic dysfunctions.