Project description:Recent studies suggest a hierarchical model in which lineage-determining factors act in a collaborative manner to select and prime cell-specific enhancers, thereby enabling signal-dependent transcription factors to bind and function in a cell type-specific manner. Consistent with this model, TLR4 signaling primarily regulates macrophage gene expression through a pre-existing enhancer landscape. However, TLR4 signaling also induces priming of ~3000 enhancer-like regions de novo, enabling visualization of intermediates in enhancer selection and activation. Unexpectedly, we find that enhancer transcription precedes local mono- and di-methylation of histone H3 lysine 4 (H3K4me1/2). H3K4 methylation at de novo enhancers is primarily dependent on the histone methyltransferases Mll1, Mll2/4 and Mll3, and is significantly reduced by inhibition of RNA polymerase II elongation. Collectively, these findings suggest an essential role of enhancer transcription in H3K4me1/2 deposition at de novo enhancers that is independent of potential functions of the resulting eRNA transcripts. ChIP-Seq and Gro-Seq profiling was performed in thioglycollate-elicited peritoneal macrophages, PU.1-/- and PUER cells treated as indicated.
Project description:Cellular differentiation is orchestrated by lineage-specific transcription factors and associates with cell type-specific epigenetic signatures. Here, we utilized stage-specific, epigenetic "fingerprints" to deduce key transcriptional regulators of a cellular differentiation process. In the model of human macrophage differentiation, we globally mapped the distribution of epigenetic enhancer marks (histone H3 lysine 4 monomethylation, histone H3 lysine 27 acetylation, and the histone variant H2AZ) and show that cell type-specific epigenetic "fingerprints" correlate with specific, de novo derived motif signatures at all differentiation stages studied (hematopoietic progenitor cell, monocyte, macrophage). We validated the novel, de novo derived, macrophage-specific enhancer signature which included ETS, CEBP, bZIP, EGR, E-Box and NFkB motifs by ChIP-sequencing for a subset of motif corresponding transcription factors (PU.1, C/EBPbeta, and EGR2) which confirmed their predicted association with differentiation-associated epigenetic changes. This study highlights the power of genome-wide epigenetic profiling studies to reveal novel functional insights. It describes the dynamic enhancer landscape of human macrophage differentiation and provides a unique resource for macrophage biologists. ChIP-seq of 3 histone marks and 3 transcription factors in human blood monocytes and macrophages
Project description:Here we have used both chromatin accessibility and enhancer activity marks to study enhancer activation and changes in transcriptional networks during the differentiation of human MSC into osteoblasts and adipocytes. We demonstrate that adipogenesis is driven by considerable remodeling of the chromatin landscape and de novo activation of enhancers, while osteogenesis involves activation of pre-established enhancers. Using machine learning algorithms for in silico modeling of transcriptional regulation we predict the repertoire of transcription factors that drive the two differentiation pathways. We show that osteoblast differentiation depends on the activation of a large and diverse transcriptional network of pro-osteogenic and anti-adipogenic transcription factors. Intriguingly, knockdown of single members of this network is sufficient to modulate differentiation in both directions, indicating that lineage-determination is a delicate balance between activities of many different transcription factors.
Project description:While cell-type-restricted enhancers are initially detected following cooperative binding of positionally-determined DNA binding transcription factors during determination/differentiation, it remains unknown whether there are preceding events in embryonic stem cells (ESCs) that are functionally important to activate cell-type-restricted enhancer networks. Here, using murine macrophages as a model, we report that, while largely devoid of characteristic enhancer marks (H3K4me1, H3K4me2, H3K27Ac, H3K27me3 and p300) in ESCs, macrophage enhancers are activated as transcription units mainly by the binding of a single, at most two, ESC transcription factors. This provides “premarking” of these enhancers, as is also observed for other cell types. In contrast, ESC-active enhancers are cooperatively bound by multiple ESC transcription factors, including Esrrb, Nanog, Oct4 and Sox2 (ENOS). Interestingly, the strength of this signature in ESCs is functionally important for subsequent robust cell-restricted enhancer activation during macrophage differentiation events, as independently demonstrated by analysis of multiple ENOS motif–deleted macrophage-restricted enhancers. The ENOS-determined location of hydroxymethylation of the enhancers in ESCs could serve as a potential molecular memory for subsequent enhancer activation in the mature macrophage. These findings suggest that the massive repertoire of cell-type-restricted enhancers are essentially hierarchically and obligatorily “barcoded” by binding of a single ESC transcription factor in ESCs, with the strength of their binding dictating enhancer activation in mature cells.
Project description:While cell-type-restricted enhancers are initially detected following cooperative binding of positionally-determined DNA binding transcription factors during determination/differentiation, it remains unknown whether there are preceding events in embryonic stem cells (ESCs) that are functionally important to activate cell-type-restricted enhancer networks. Here, using murine macrophages as a model, we report that, while largely devoid of characteristic enhancer marks (H3K4me1, H3K4me2, H3K27Ac, H3K27me3 and p300) in ESCs, macrophage enhancers are activated as transcription units mainly by the binding of a single, at most two, ESC transcription factors. This provides “premarking” of these enhancers, as is also observed for other cell types. In contrast, ESC-active enhancers are cooperatively bound by multiple ESC transcription factors, including Esrrb, Nanog, Oct4 and Sox2 (ENOS). Interestingly, the strength of this signature in ESCs is functionally important for subsequent robust cell-restricted enhancer activation during macrophage differentiation events, as independently demonstrated by analysis of multiple ENOS motif–deleted macrophage-restricted enhancers. The ENOS-determined location of hydroxymethylation of the enhancers in ESCs could serve as a potential molecular memory for subsequent enhancer activation in the mature macrophage. These findings suggest that the massive repertoire of cell-type-restricted enhancers are essentially hierarchically and obligatorily “barcoded” by binding of a single ESC transcription factor in ESCs, with the strength of their binding dictating enhancer activation in mature cells.
Project description:While cell-type-restricted enhancers are initially detected following cooperative binding of positionally-determined DNA binding transcription factors during determination/differentiation, it remains unknown whether there are preceding events in embryonic stem cells (ESCs) that are functionally important to activate cell-type-restricted enhancer networks. Here, using murine macrophages as a model, we report that, while largely devoid of characteristic enhancer marks (H3K4me1, H3K4me2, H3K27Ac, H3K27me3 and p300) in ESCs, macrophage enhancers are activated as transcription units mainly by the binding of a single, at most two, ESC transcription factors. This provides “premarking” of these enhancers, as is also observed for other cell types. In contrast, ESC-active enhancers are cooperatively bound by multiple ESC transcription factors, including Esrrb, Nanog, Oct4 and Sox2 (ENOS). Interestingly, the strength of this signature in ESCs is functionally important for subsequent robust cell-restricted enhancer activation during macrophage differentiation events, as independently demonstrated by analysis of multiple ENOS motif–deleted macrophage-restricted enhancers. The ENOS-determined location of hydroxymethylation of the enhancers in ESCs could serve as a potential molecular memory for subsequent enhancer activation in the mature macrophage. These findings suggest that the massive repertoire of cell-type-restricted enhancers are essentially hierarchically and obligatorily “barcoded” by binding of a single ESC transcription factor in ESCs, with the strength of their binding dictating enhancer activation in mature cells.
Project description:While cell-type-restricted enhancers are initially detected following cooperative binding of positionally-determined DNA binding transcription factors during determination/differentiation, it remains unknown whether there are preceding events in embryonic stem cells (ESCs) that are functionally important to activate cell-type-restricted enhancer networks. Here, using murine macrophages as a model, we report that, while largely devoid of characteristic enhancer marks (H3K4me1, H3K4me2, H3K27Ac, H3K27me3 and p300) in ESCs, macrophage enhancers are activated as transcription units mainly by the binding of a single, at most two, ESC transcription factors. This provides “premarking” of these enhancers, as is also observed for other cell types. In contrast, ESC-active enhancers are cooperatively bound by multiple ESC transcription factors, including Esrrb, Nanog, Oct4 and Sox2 (ENOS). Interestingly, the strength of this signature in ESCs is functionally important for subsequent robust cell-restricted enhancer activation during macrophage differentiation events, as independently demonstrated by analysis of multiple ENOS motif–deleted macrophage-restricted enhancers. The ENOS-determined location of hydroxymethylation of the enhancers in ESCs could serve as a potential molecular memory for subsequent enhancer activation in the mature macrophage. These findings suggest that the massive repertoire of cell-type-restricted enhancers are essentially hierarchically and obligatorily “barcoded” by binding of a single ESC transcription factor in ESCs, with the strength of their binding dictating enhancer activation in mature cells.