Genomic Determinants of Hematopoietic Progenitor Sensitivity to Innate Immune Signaling

• Published in: Blood 2023-11, Vol.142 (Supplement 1), p.5577-5577
• Main Authors: Tran, Vu L., Liu, Peng, Soukup, Alexandra A., Kopp, Audrey, Schoff, Bjorn M., Mattina, Ashley E., Jung, Mabel M., Brand, Marjorie, Johnson, Kirby D., Bresnick, Emery H.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2023-186320

Innate immune processes impact diverse hematopoietic stem and progenitor cell (HSPC) functions, yet how innate immune signaling networks are sensed by HSPC genomes and how HSPC genomic activity alters cell responsiveness to innate immune regulators are not fully understood. We demonstrated that E14.5 primary (-77 -/-) and immortalized (hi-77 -/-) GATA2-deficient fetal progenitors from Gata2 -77 enhancer deletion mice upregulate Interferon-gamma (IFNγ) and Toll-like receptor (TLR) signaling components (Johnson et al. JEM 2020) and are hypersensitive to IFNγ and TLR signaling (Tran et al. iScience 2023). Combinatorial signaling involving both pathways regulates genes that are not regulated by individual pathways and amplifies responses beyond that induced by single pathways. Innate immune-activated genes harbor motifs for signal-dependent transcription factors, including the ETS factor PU.1, and GATA2 deficiency elevates PU.1 activity to upregulate B-lineage and myeloid genes (Jung et al. JCI 2023). We hypothesize that PU.1 links innate immune signaling networks and HSPC genome control. In new multi-omic studies, we asked if PU.1 is required to sense exclusively IFNγ or TLR signaling, both pathways independently or combinatorially, or is not essential. We used hi-77 -/- progenitors lacking a PU.1 enhancer ( Spi1URE-/-) with ~2-fold lower PU.1 vs. control hi-77 -/- progenitors. RNA-seq was conducted with hi-77 -/- and hi-77 -/-; Spi1URE-/- progenitors, with or without IFNγ, TLR1/2 agonist Pam 3CSK 4, or both agents for 4 h. hi-77 -/-; Spi1URE-/- progenitors lost the responsiveness of 27 TLR-activated genes and retained the responsiveness of 6 TLR-activated genes. 80% of IFNγ-activated genes (115 of 144) retained IFNγ-responsiveness when PU.1 was reduced. In hi-77 -/-; Spi1URE-/- progenitors, 68.2% (148 of 217 genes) retained their responsiveness to combinatorial signaling. These studies revealed the disproportionate importance of PU.1 for TLR- vs. IFNγ-mediated transcriptional control and a PU.1 requirement for combinatorial signaling at the majority of loci. Elevated IFNγ and TLR1/2 signaling in GATA2-deficient fetal progenitors is associated with increased monocytic and reduced granulocytic progenitors (Johnson et al. JEM 2020; Blood Adv 2022). Ablation of Irf8, encoding an IFNγ pathway component, partially normalizes the granulocytic progenitor deficit (Johnson et al. Blood Adv. 2022). Since GATA2 deficiency creates crosstalk between IFNγ and TLR1/2 pathwa