NFκB dynamics determine the stimulus-specificity of epigenomic reprogramming in macrophages

The epigenome defines the cell type, but also possesses plasticity to tune gene expression in the context of extracellular cues. This tuning is evident in immune sentinel cells such as macrophages, which respond to pathogens and cytokines with phenotypic shifts driven by epigenomic reprogramming. Recent studies indicate that this reprogramming arises from the activity of transcription factors including nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). NFκB binds not only to available enhancers but may also produce de novo enhancers in previously silent areas of the genome. Here, we show that NFκB reprograms the macrophage epigenome in a stimulus-specific manner, in response only to a subset of pathogen-derived stimuli. The basis for these surprising differences lies in the stimulus-specific temporal dynamics of NFκB activity. In response to different stimuli, NFκB enters the nucleus with variable speed, amplitude, and duration, and may oscillate between the nucleus and cytoplasm. These dynamical features combine to specify the identity and dose of a given stimulus. We demonstrate through live cell imaging, mathematical modeling, and genetic perturbations that NFκB promotes open chromatin and formation of de novo enhancers most strongly when its dynamics are non-oscillatory. These de novo enhancers result in the activation of additional response genes. We propose a mechanistic paradigm in which the temporal dynamics of transcription factors are a key determinant of their capacity to control epigenomic reprogramming, thus enabling the formation of stimulus-specific memory in innate immune sentinel cells. Sequencing data from murine bone marrow-derived macrophages, comparing different TLR stimuli and using genetic perturbations of NFκB signaling dynamics. H3K4me1 ChIP-seq (41 samples), ATAC-seq (36 samples), mRNA-seq (19 samples).