Human iPSCs-based modeling unveils a dominant role of SETBP1 mutation in shaping stable chromatin accessibility landscape in GATA2 deficiency

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.