3010 – MOLECULAR DETERMINANTS OF INNATE IMMUNE SIGNAL-DEPENDENT GENOME RESPONSIVENESS IN HEMATOPOIETIC PROGENITOR CELLS

GATA2 coding and noncoding germline mutations cause GATA2 deficiency syndrome, often leading to myelodysplastic syndrome and acute myeloid leukemia. We demonstrated that GATA2 deficiency in murine fetal liver progenitors resulting from loss of Gata2 -77 enhancer upregulates components of Interferon-gamma (IFNg) and Toll-like receptor (TLR) signaling pathways. Using a genetic rescue system, we demonstrated that GATA2-deficient fetal progenitors are hypersensitive to IFNg and TLR1/2 agonist through signaling crosstalk to establish an aberrant transcriptional state. This elevated innate immune signaling is associated with disrupted hematopoiesis and retention of monocytic differentiation ex vivo. GATA2 deficiency elevated expression of select B-lineage and myeloid genes via a PU.1-dependent mechanism. To test the hypothesis that PU.1 is required to establish an ectopic signaling state in GATA2-deficient progenitors, we deleted Spi1 -14 kb enhancer, reducing PU.1 expression ∼50%, and tested whether PU.1 is critical, contributory, or not required for IFNg- and TLR-dependent genomic responses. RNA-seq analysis revealed that PU.1 loss abrogated TLR1/2-dependent transcriptional regulation. By contrast, PU.1 loss attenuated certain, but not all, IFNg-mediated transcriptional responses or responses to synergistic signaling. Multiomic studies are parsing GATA2 and PU.1 target genes as signal-dependent or -independent and establishing mechanisms rendering a given gene regulated by GATA2, PU.1, individual pathways, and/or synergistic signaling. In aggregate, these studies support a model in which GATA2 levels dictate genome responsiveness to the innate immune signaling milieu, and elucidating the mechanisms will unveil new concepts of how hematopoietic regulators dictate genome responsiveness to a dynamically changing signaling environment in physiological and pathologic contexts. GATA2 coding and noncoding germline mutations cause GATA2 deficiency syndrome, often leading to myelodysplastic syndrome and acute myeloid leukemia. We demonstrated that GATA2 deficiency in murine fetal liver progenitors resulting from loss of Gata2 -77 enhancer upregulates components of Interferon-gamma (IFNg) and Toll-like receptor (TLR) signaling pathways. Using a genetic rescue system, we demonstrated that GATA2-deficient fetal progenitors are hypersensitive to IFNg and TLR1/2 agonist through signaling crosstalk to establish an aberrant transcriptional state. This elevated innate immune signaling is associated with disrupted hematopoiesis and retention of monocytic differentiation ex vivo. GATA2 deficiency elevated expression of select B-lineage and myeloid genes via a PU.1-dependent mechanism. To test the hypothesis that PU.1 is required to establish an ectopic signaling state in GATA2-deficient progenitors, we deleted Spi1 -14 kb enhancer, reducing PU.1 expression ∼50%, and tested whether PU.1 is critical, contributory, or not required for IFNg- and TLR-dependent genomic responses. RNA-seq analysis revealed that PU.1 loss abrogated TLR1/2-dependent transcriptional regulation. By contrast, PU.1 loss attenuated certain, but not all, IFNg-mediated transcriptional responses or responses to synergistic signaling. Multiomic studies are parsing GATA2 and PU.1 target genes as signal-dependent or -independent and establishing mechanisms rendering a given gene regulated by GATA2, PU.1, individual pathways, and/or synergistic signaling. In aggregate, these studies support a model in which GATA2 levels dictate genome responsiveness to the innate immune signaling milieu, and elucidating the mechanisms will unveil new concepts of how hematopoietic regulators dictate genome responsiveness to a dynamically changing signaling environment in physiological and pathologic contexts.