Project description:Clinical GATA2 deficiency syndromes arise from germline haploinsufficiency inducing mutations in GATA2, resulting in immunodeficiency that evolves to myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML). How GATA2 haploinsufficiency disrupts the function and transcriptional network of hematopoietic stem/progenitors (HSCs/HSPCs) to facilitate the shift from immunodeficiency sequalae to pre-leukemia is poorly characterised. Using a conditional mouse model harboring a single allele deletion of Gata2 when HSCs emerge in utero, we identify pervasive defects in HSPC differentiation from young adult Gata2 haploinsufficient mice during B-cell maturation, early erythroid specification, megakaryocyte maturation to platelets and inflammatory cell generation. Gata2 haploinsufficiency abolishes HSC self-renewal and multi-lineage differentiation capacity following transplantation. These alterations closely associate with deregulated DNA damage responses and inflammatory signalling conveyed from Gata2 haploinsufficient HSCs. We also identify functional interplay between Gata2 and Asxl1, a driver of DNA damage and inflammation and, notably, a recurrent secondary mutation found in GATA2 haploinsufficiency disease progression to MDS/AML. shRNA mediated knockdown of Asxl1 in Gata2 haploinsufficient HSPCs led to a differentiation block in committed progenitor formation beyond that in Gata2 haploinsufficient HSPCs. By analysis of HSCs from young adult compound Gata2/Asxl1 haploinsufficient mice, we discover hyperproliferation of double haploinsufficent HSCs, which are also functionally compromised in transplantation compared to their single haploinsufficient counterparts. Through both Gata2/Asxl1 dependent and unique transcriptional programs, HSCs from young adult compound Gata2/Asxl1 haploinsufficient mice fortify deregulated DNA damage responses and inflammatory signalling in HSCs initiated in Gata2 haploinsufficient mice and establish a broad pre-leukemic program. Our data reveal how Gata2 haploinsufficiency initially drives deregulation of HSC genome integrity and suggest the mechanisms of how secondary mutations like ASXL1 take advantage of HSC genomic instability to nurture a pre-leukemic state in GATA2 haploinsufficiency syndromes.

Project description:Background and Purpose: Constitutional GATA2 deficiency caused by heterozygous germline GATA2 mutation has a broad spectrum of clinical phenotypes including systemic infections, lymphedema, cytopenias, MDS and AML. A comprehensive profiling of transcriptome of hematopoiesis in GATA2 deficiency is currently lacking. Methods: We performed single-cell RNA sequencing of sorted bone marrow CD34+ hematopoietic stem and progenitor cells (HSPCs) from eight GATA2 deficiency patients, who had various well characterized GATA2 mutations and clinically manifest myelodysplasia. We characterized transcriptomes in lineages, computationally defined cells with chromosomal abnormalities, and described gene expression of these cells. Results: Mapping patients’ cells onto normal hematopoiesis, we observed preferred deficiency in lymphoid and myeloid progenitors, which also was evidenced in loss of heterogeneity in gene correlations. HSPCs in patients exhibited distinct gene expression pattern and gene coexpression pattern compared with its counterparts in healthy donors. Distinct lineages show different transcriptional profiles resulting from GATA2 mutations. HSCs in patients exhibited dysregulated genes in apoptosis, cell cycle and quiescence, and had increased expression of erythroid/megakaryocytic priming programs and decreased lymphoid priming programs. Thus, the prominent deficiency in myeloid/lymphoid lineages in GATA2 deficiency was partly due to expression of aberrant gene programs in HSCs prior to lineage commitment. We computationally defined cells with chromosomal abnormalities and described gene expression of these cells. DNA repair genes were downregulated in trisomy 8 cells, possibly rendering these cells vulnerable to second-hit somatic mutations and additional chromosomal abnormalities. Cells with complex cytogenetics had defects in multi-lineage differentiation and cell cycle. Conclusion: Germline GATA2 mutations modulate gene expression and change gene coexpression patterns. Distinct lineages show different transcriptional profiles resulting from GATA2 mutations. The prominent deficiency in myeloid/lymphoid lineages in GATA2 deficiency was partly due to expression of aberrant gene programs in HSCs prior to lineage commitment.

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MECOM promotes leukemia progression and inhibits mast cell differentiation through functional competition with GATA2 (CordBlood_RNA-seq)

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