Project description:The integrated activity of cis-regulatory elements fine-tunes transcriptional programs of mammalian cells by recruiting cell type–specific as well as ubiquitous transcription factors (TFs). Despite their key role in modulating transcription, enhancers are still poorly characterized at the molecular level, and their limited DNA sequence conservation in evolution and variable distance from target genes make their unbiased identification challenging. The coexistence of high mono-methylation and low tri-methylation levels of lysine 4 of histone H3 is considered a signature of enhancers, but a comprehensive view of histone modifications associated to enhancers is still lacking. By combining chromatin immunoprecipitation (ChIP) with mass spectrometry, we investigated cis-regulatory regions in macrophages to comprehensively identify histone marks specifically associated with enhancers, and to profile their dynamics after transcriptional activation elicited by an inflammatory stimulation. The intersection of the proteomics data with ChIP-seq and RNA-seq analyses revealed the existence of novel subpopulations of enhancers, marked by specific histone modification signatures: specifically, H3K36me2/K4me1 marks transcribed enhancers, while H3K36me3/K4me1 and H3K79me2/K4me1 combinations mark distinct classes of intronic enhancers. Thus, our MS analysis of functionally distinct genomic regions revealed the combinatorial code of histone modifications, highlighting the potential of proteomics in addressing fundamental questions in epigenetics.
Project description:Evolutionary alterations to cis-regulatory sequences are likely to cause adaptive phenotypic complexity, through orchestrating changes in cellular proliferation, identity and communication. For non-model organisms with adaptive key-innovations, patterns of regulatory evolution have been predominantly limited to targeted sequence-based analyses. Chromatin-immunoprecipitation with high-throughput sequencing (ChIP-seq) is a technology that has only been used in genetic model systems and is a powerful experimental tool to screen for active cis-regulatory elements. Here, we show that it can also be used in ecological model systems and permits genome-wide functional exploration of cis-regulatory elements. As a proof of concept, we use ChIP-seq technology in adult fin tissue of the cichlid fish Oreochromis niloticus to map active promoter elements, as indicated by occupancy of trimethylated Histone H3 Lysine 4 (H3K4me3). The fact that cichlids are one of the most phenotypically diverse and species-rich families of vertebrates could make them a perfect model system for the further in-depth analysis of the evolution of transcriptional regulation. examination of H3K4me3 in adult fin tissue of the Nile tilapia (Oreochromis niloticus)
Project description:The evolution of human anatomical features likely involved changes in gene regulation during development. However, the nature and extent of human specific developmental regulatory functions remain unknown. We obtained a genome-wide view of cis regulatory evolution in human embryonic tissues by comparing the histone modification H3K27ac, which provides a quantitative readout of promoter and enhancer activity, during human, rhesus, and mouse limb development. Based on increased H3K27ac, we find that 13% of promoters and 11% of enhancers have gained activity on the human lineage since the human-rhesus divergence. These gains largely arose by modification of ancestral regulatory activities in the limb or potential co-option from other tissues and are likely to have heterogeneous genetic causes. Most enhancers that exhibit gain of activity in humans originated in mammals. Gains at promoters and enhancers in the human limb are associated with increased gene expression, suggesting they include molecular drivers of human morphological evolution. ChIP-Seq and RNA-Seq of autopod tissue of developing limb buds of Human (E33-E47), rhesus (E31-E36), and mouse (E10.5-E13.5). No raw data are provided for human samples. Human alignments were anonymized by removing sequence information and converting to bed format.
Project description:Evolutionary alterations to cis-regulatory sequences are likely to cause adaptive phenotypic complexity, through orchestrating changes in cellular proliferation, identity and communication. For non-model organisms with adaptive key-innovations, patterns of regulatory evolution have been predominantly limited to targeted sequence-based analyses. Chromatin-immunoprecipitation with high-throughput sequencing (ChIP-seq) is a technology that has only been used in genetic model systems and is a powerful experimental tool to screen for active cis-regulatory elements. Here, we show that it can also be used in ecological model systems and permits genome-wide functional exploration of cis-regulatory elements. As a proof of concept, we use ChIP-seq technology in adult fin tissue of the cichlid fish Oreochromis niloticus to map active promoter elements, as indicated by occupancy of trimethylated Histone H3 Lysine 4 (H3K4me3). The fact that cichlids are one of the most phenotypically diverse and species-rich families of vertebrates could make them a perfect model system for the further in-depth analysis of the evolution of transcriptional regulation.
Project description:We describe, MARGE, Model-based Analysis of the Regulation of Gene Expression, a robust methodology that leverages a large library of genome-wide H3K27ac ChIP-seq profiles to predict key regulated genes and cis-regulatory regions in human or mouse. MARGE adopts a gene centric approach to define a regulatory potential that summarizes the aggregate activity of multiple cis-regulatory elements on each gene. This model is effective in describing cis-regulatory activity and, unlike the super-enhancer based approach, is highly predictive of gene expression changes in response to BET-bromodomain inhibitors. We show that linear combinations of H3K27ac defined regulatory potentials, selected from an extensive database of published H3K27ac profiles, can accurately model diverse gene sets derived from differential gene expression experiments. In addition, we demonstrate a novel semi-supervised learning approach for identifying transcription factor binding sites associated with the set of transcription factors that regulate the gene set. MARGE leverages published H3K27ac ChIP-seq data to enhance the interpretation of newly generated H3K27ac ChIP-seq profiles. MARGE can also be used to analyze gene expression studies, without the production of matched H3K27ac ChIP-seq data. Identifying genomic profiles of histone modification H3K27ac in LNCaP-abl cell line after siRNA knock down of a series of gene factors.
Project description:While genome sequencing has identified numerous non-coding alterations between primate species, which of these are regulatory and potentially relevant to the evolution of the human brain is unclear. Here, we annotate cis-regulatory elements (CREs) in the human, rhesus macaque and chimpanzee genome using ChIP-sequencing in different anatomical parts of the adult brain. We find high similarity in the genomic positioning of CREs between rhesus macaque and humans, suggesting that the majority of these elements were already present in a common ancestor 25 million years ago. Most of the observed regulatory changes between humans and rhesus macaque occurred prior to the ancestral separation of humans and chimpanzee, leaving a modest set of regulatory elements with predicted human-specificity. Our data refine previous predictions and hypotheses on the consequences of genomic changes between primate species, and allow the identification of regulatory alterations relevant to the evolution of the brain. ChIP-Sequencing for H3K27ac on 8 distinct brain regions from human (three biological replicates per brain region), chimpanzee (two biological replicates per brain region) and rhesus macaque (three biological replicates per brain region).
Project description:Gene regulation can evolve either by cis-acting local changes to regulatory element DNA sequences or by global changes to the trans-acting regulatory environment; however, the modes favored during recent human evolution are unknown. To date, studies investigating gene regulatory divergence between closely-related species have produced limited estimates on the relative contributions of cis and trans effects on DNA regulatory element activities at a global-scale. By leveraging a comparative ATAC-STARR-seq framework, we identified 10,779 regulatory regions with divergent activity in cis and 10,608 regulatory regions with divergent activity in trans between human and rhesus macaque lymphoblastoid cell lines (LCLs). This revealed substantially more trans effects than predicted and indicates trans-regulatory mechanisms play a larger role in human evolution than previously expected. We also discover that most species-specific regulatory elements (67%) diverge in both cis and trans, suggesting these two mechanisms jointly drive divergent regulatory activity in a single sequence.
Project description:Dermal fibroblasts from human, rhesus macaque, mouse and rat with and without dsRNA (poly I:C) stimulation (1ug/mL for 4 hours).<br>The innate immune response - the expression programme that is initiated once a pathogen is sensed - is known to be variable among responding cells, as well as to rapidly evolve in the course of mammal evolution. To study the transcriptional divergence and cell-to-cell variability of this response, we stimulated dermal fibroblast cells from two primates (human and macaque) and two rodents (mouse and rat) with dsRNA - a mimic of viral RNA that elicits a rapid innate immune response. Subsequently, we profiled the response using bulk RNA-seq, scRNA-seq and ChIP-seq across the four species and across different time points.