A Stringent Systems Approach Uncovers Gene-Specific Mechanisms Regulating Inflammation [ATAC-seq]
ABSTRACT: Much has been learned about transcriptional cascades and networks from large-scale systems analyses of high-throughput data sets. However, analysis methods that optimize statistical power through simultaneous evaluation of thousands of ChIP-seq peaks or differentially expressed genes possess substantial limitations in their ability to uncover mechanistic principles of transcriptional control. By examining nascent transcript RNA-seq, ChIP-seq, and binding motif data sets from lipid A-stimulated macrophages with increased attention to the quantitative distribution of signals, we identified unexpected relationships between the in vivo binding properties of inducible transcription factors, motif strength, and transcription. Furthermore, rather than emphasizing common features of large clusters of co-regulated genes, our results highlight the extent to which unique mechanisms regulate individual genes with key biological functions. Our findings demonstrate the mechanistic value of stringent interrogation of well-defined sets of genes as a complement to broader systems analyses of transcriptional cascades and networks. Bone marrow-derived macrophages were stimulated with lipid A for 0 or 120 minutes. Chromatin was treated with Tn5 transposase to measure DNA accessibility
Project description:To identify conserved TNFα-induced changes in chromatin-accessibility in mammals, we performed ATAC-seq in primary vascular endothelial cells (ECs) isolated from the aortas of human (HAEC), mouse (MAEC) and cow (BAEC), before and after TNFα. We overlay our data with multi-species NF-κB binding data and identify multiple modes of NF-κB-chromatin interactions that are conserved during mammalian TNFα response. Our cross-species approach identifies conserved changes in chromatin-accessibility at NF-κB binding sites that are disease-relevant and essential during mammalian acute inflammation.
Project description:Genome Wide Association Studies (GWAS) have been successful in yielding >60 loci for Systemic Lupus Erythematosus (SLE). However, it is known that GWAS just reports genomic signals and not necessarily the precise localization of culprit genes, with eQTL efforts only able to infer causality to a minority of such loci. Thus, we sought to carry out physical and direct ‘variant to gene mapping’ by integrating results from high-throughput chromatin conformation capture and ATAC-seq assays. This experiment refers to the ATAC-seq part of our work. To determine informative proxy SNPs for each of the SLE GWAS sentinel loci, we generated ATAC-seq open chromatin maps for primary human T Follicular Helper (TFH) cells from tonsils of healthy volunteers (3 biological replicates), a model relevant to SLE as TFH operate upstream of the activation of pathogenic autoantibody-producing B cells during the disease. We also generated open chromatin maps for naive CD4-positive helper T cells (3 biological replicates).
Project description:We report the IFN-induced dynamics in murine splenic B cells. Male C57BL/6 mice were injected subcutaneously with 10,000U IFNa and spleens were removed at 90min. B cells were negatively isolated using magnetic beads and profiled for the chromatin configuration by ATAC-seq. Profilings of chromatin configuration by ATAC-seq (0 and 90min, biological duplicate for each).
Project description:Activated T cells differentiate into functional subsets which require distinct metabolic programs. Glutaminase (GLS) converts glutamine to glutamate to provide substrate for the tricarboxylic acid cycle and epigenetic reactions and here we identify a key role for GLS in T cell activation and specification. Though GLS-deficiency diminished T cell activation, proliferation and impaired differentiation of Th17 cells, loss of GLS also increased Tbet and Interferon-γ expression and CD4 Th1 and CD8 CTL effector cell differentiation. These changes were mediated by differentially altered gene expression and chromatin accessibility, leading to increased sensitivity of Th1 cells to IL-2 mediated mTORC1 signaling. In vivo, GLS-null T cells failed to drive a Th17 mediated Graft-vs-Host Disease model. Transient inhibition of GLS, however, increased Th1 and CTL T cell numbers in viral and chimeric antigen receptor models. Glutamine metabolism thus has distinct roles to promote Th17 but constrain Th1 and CTL effector cell differentiation.
Project description:To determine the ability of HNF4A and GATA6 to drive open chromatin formation, either HNF4A or GATA6 were overexpressed in normal oesophageal Het1A cells and ATAC-seq was performed.