Dual Roles for Ikaros in Regulation of Macrophage Chromatin State and Inflammatory Gene Expression

J Immunol. 2018 Jul 15;201(2):757-771. doi: 10.4049/jimmunol.1800158. Epub 2018 Jun 13.


Macrophage activation by bacterial LPS leads to induction of a complex inflammatory gene program dependent on numerous transcription factor families. The transcription factor Ikaros has been shown to play a critical role in lymphoid cell development and differentiation; however, its function in myeloid cells and innate immune responses is less appreciated. Using comprehensive genomic analysis of Ikaros-dependent transcription, DNA binding, and chromatin accessibility, we describe unexpected dual repressor and activator functions for Ikaros in the LPS response of murine macrophages. Consistent with the described function of Ikaros as transcriptional repressor, Ikzf1-/- macrophages showed enhanced induction for select responses. In contrast, we observed a dramatic defect in expression of many delayed LPS response genes, and chromatin immunoprecipitation sequencing analyses support a key role for Ikaros in sustained NF-κB chromatin binding. Decreased Ikaros expression in Ikzf1+/- mice and human cells dampens these Ikaros-enhanced inflammatory responses, highlighting the importance of quantitative control of Ikaros protein level for its activator function. In the absence of Ikaros, a constitutively open chromatin state was coincident with dysregulation of LPS-induced chromatin remodeling, gene expression, and cytokine responses. Together, our data suggest a central role for Ikaros in coordinating the complex macrophage transcriptional program in response to pathogen challenge.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Cell Differentiation
  • Chromatin / metabolism*
  • Chromatin Assembly and Disassembly
  • Gene Expression Regulation / immunology
  • Humans
  • Ikaros Transcription Factor / genetics
  • Ikaros Transcription Factor / metabolism*
  • Inflammation / genetics
  • Inflammation / immunology*
  • Lipopolysaccharides / immunology
  • Macrophages / physiology*
  • Mice
  • Mice, Knockout
  • Promoter Regions, Genetic
  • Protein Binding
  • RAW 264.7 Cells


  • Chromatin
  • Lipopolysaccharides
  • Ikaros Transcription Factor