Downregulation of SP‐R210L Alters the Macrophage Epigenetic Chromatin Landscape Associated with Changes in Transcription Factor Binding

Abstract

Alveolar macrophages are the first immune cells to come into contact with air‐borne pathogens such as influenza. Previous studies demonstrated that the surfactant protein A (SP‐A) receptor, SP‐R210, also known as MYO18A, regulates the immune functions of macrophages through the action of two isoforms; a long form SP‐R210L(L), and a short form SP‐R210S(S). Stable knockdown of L in RAW264.7 cells (abbreviated as DN) revealed alterations in mRNA expression of innate immune receptors and responsiveness to various inflammatory stimuli. To elucidate the intrinsic functions of the L isoform, the present study addressed the hypothesis that L modulates macrophage gene transcription through epigenetic modification of chromatin. We thus utilized chromatin immunoprecipitation and sequencing (ChIP‐seq) to determine the impact of L depletion on histone modification marks H3K4me3, H3K9me3, and H3K27me3 and binding of transcription factors PU.1 and NFκB subunit RelA, which regulate macrophage differentiationand inflammatory responses, respectively. Pulled‐down sequences were visualized on the UCSC genome browser to identify the spatial relation between enriched sequences. This analysis showed reduced PU.1 binding at genes associated with macrophage differentiation and intercellular communication between innate and adaptive immune cells, such as interleukin 18 (IL‐18) and colony‐stimulating factor receptors (CSF1R, CSF2RB) in DN cells. Additionally, differences in PU.1 binding were reflected in similar suppression of H3K4me3 marks in DN cells. Further analysis by ChIPpeakAnno and ChIPseeker and ingenuity pathway analysis, however, revealed enrichment in genes that regulate TNFα and interferon (IFN) signaling in DN cells. Collectively, these findings support the idea that the L isoform of SP‐R210 regulates chromatin architecture and accessibility of transcription factors at genes with discrete roles in macrophage differentiation and activation.Support or Funding InformationThis work was supported by HL128746, The Children's Miracle Network, and the Department of Pediatrics, Penn State University College of MedicineThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.