No abstract

SUMMARY Hematopoietic development requires the transcription factor GATA-2, and GATA-2 mutations cause diverse pathologies including leukemia. GATA-2-regulated enhancers regulate Gata2 expression in hematopoietic stem/progenitor cells and control hematopoiesis. The +9.5 kb enhancer activates transcription in endothelium and hematopoietic stem cells (HSCs), and its deletion abrogates HSC generation. The −77 kb enhancer activates transcription in myeloid progenitors, and its deletion impairs differentiation. Since +9.5−/− embryos are HSC-deficient, it was unclear whether the +9.5 functions in progenitors or if GATA-2 expression in progenitors solely requires −77. We further dissected the mechanisms using −77;+9.5 compound heterozygous (CH) mice. The embryonic lethal CH mutation depleted megakaryocyte-erythrocyte progenitors (MEPs). While the +9.5 suffices for HSC generation, the −77 and +9.5 must reside on one allele to induce MEPs. The −77 generated Burst Forming Unit-Erythroid through induction of GATA-1 and other GATA-2 targets. The enhancer circuits controlled signaling pathways that orchestrate a GATA factor-dependent blood development program.

By inducing the generation and function of hematopoietic stem and progenitor cells, the master regulator of hematopoiesis GATA-2 controls the production of all blood cell types. Heterozygous GATA2 mutations cause immunodeficiency, myelodysplastic syndrome, and acute myeloid leukemia. GATA2 disease mutations commonly disrupt amino acid residues that mediate DNA binding or cis-elements within a vital GATA2 intronic enhancer, suggesting a haploinsufficiency mechanism of pathogenesis. Mutations also occur in GATA2 coding regions distinct from the DNA-binding carboxyl-terminal zinc finger (C-finger), including the amino-terminal zinc finger (N-finger), and N-finger function is not established. Whether distinct mutations differentially impact GATA-2 mechanisms is unknown. Here, we demonstrate that N-finger mutations decreased GATA-2 chromatin occupancy and attenuated target gene regulation. We developed a genetic complementation assay to quantify GATA-2 function in myeloid progenitor cells from Gata2 −77 enhancer-mutant mice. GATA-2 complementation increased erythroid and myeloid differentiation. While GATA-2 disease mutants were not competent to induce erythroid differentiation of Lin−Kit+ myeloid progenitors, unexpectedly, they promoted myeloid differentiation and proliferation. As the myelopoiesis-promoting activity of GATA-2 mutants exceeded that of GATA-2, GATA2 disease mutations are not strictly inhibitory. Thus, we propose that the haploinsufficiency paradigm does not fully explain GATA-2–linked pathogenesis, and an amalgamation of qualitative and quantitative defects instigated by GATA2 mutations underlies the complex phenotypes of GATA-2–dependent pathologies.