Global STARR-seq library profiling of open chromatin regions in livers of mice treated with the nuclear receptor CAR (Nr1i3) agonist ligand TCPOBOP, in livers of control male mice and in livers of control female mice. [G187_global]
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ABSTRACT: Massively parallel reporter assays (MPRA) are widely used to discover functional enhancers but have largely been limited to transfected cell models, which are confounded by vector-induced innate immune responses and lack the physiologically relevant cellular and endogenous hormonal context and chromatin environment of complex mammalian tissues. Here, we combine hydrodynamic injection with a modified STARR-seq-based MPRA to determine condition-specific enhancer activity in mouse liver at scale. Strong liver enhancer activity was observed with STARR-seq libraries containing an Albumin minimal promoter but not when using a Super Core promoter or an origin of replication promoter. Analysis of a global STARR-seq library, comprised of ~50,000 genomic sequences released by DNase-I digestion of mouse liver nuclei, identified condition-specific enhancers and revealed strong correlations between liver enhancer activity and the chromatin state of the corresponding endogenous genomic regions.
Project description:Massively parallel reporter assays are widely used to discover functional enhancers but have largely been limited to transfected cell models, which are confounded by vector-induced innate immune responses and lack the physiologically relevant cellular and endogenous hormonal context and chromatin environment of complex mammalian tissues. Here, we combine hydrodynamic injection with a modified STARR-seq-based MPRA to determine condition-specific enhancer activity in mouse liver at scale. Strong liver enhancer activity was observed with STARR-seq libraries containing an Albumin minimal promoter but not when using a Super Core promoter or an origin of replication promoter. We prepared a focused STARR-seq library comprised of 100 PCR-amplified open chromatin regions nearby genes showing sex-biased expression or responsiveness to TCPOBOP, a xenobiotic and agonist ligand of the nuclear receptor CAR (Nr1i3). We assayed STARR-seq activity for the 100 genomic regions in male liver, in female liver and in TCPOBOP-treated male liver to quantitatively measure their intrinsic transcriptional activity under the 3 indicated biological conditions, and thereby identified enhancers whose activity is sex-dependent or xenobiotic-responsive.
Project description:Massively parallel reporter assays (MPRA) are widely used to discover functional enhancers but have largely been limited to transfected cell models. Here, we combine hydrodynamic injection with a modified STARR-seq-based MPRA to determine condition-specific enhancer activity in mouse liver at scale, and we examine how different promoters affect STARR-seq reporter activity. Strong liver enhancer activity was observed with STARR-seq libraries containing an Albumin minimal promoter but not when using a Super Core promoter or an origin of replication (ORI) promoter. This work is part of a larger study where we prepare a global STARR-seq library, comprised of ~50,000 genomic sequences released by DNase-I digestion of mouse liver nuclei, and where we identify condition-specific enhancers with strong correlations between liver enhancer activity and the chromatin state of the corresponding endogenous genomic regions.
Project description:STARR-seq reporter activity of plasmid libraries delivered to mouse liver by hydrodynamic injection: In vivo MPRA assay for enhancer activity
Project description:Genomic enhancers are important regulators of gene expression, but their identification is a challenge and methods depend on indirect measures of activity. We developed a method termed STARR-seq to directly and quantitatively assess enhancer activity for millions of candidates from arbitrary sources of DNA, enabling screens across entire genomes. When applied to the Drosophila genome, STARR-seq identifies thousands of cell type-specific enhancers across a broad continuum of strengths, linking differential gene expression to differences in enhancer activity and creating a genome-wide quantitative enhancer map. This map reveals the highly complex regulation of transcription, with several independent enhancers for both developmental regulators and ubiquitously expressed genes. STARR-seq can be used to identify and quantitate enhancer activity in other eukaryotes, including human. STARR-seq was performed in S2 and OSC cells with paired-end sequencing in two replicates and respective inputs. DHS-seq was done with single-end sequencing in two replicates for S2 and OSC cells. RNA-seq was performed with a strand-specific protocol using single-end sequencing in two replicates within S2 and OSC cells. STARR-seq was also performed in HeLa cells with single-end sequencing with a respective input.
Project description:The spatiotemporal specific gene expression is regulated by cell type-specific regulatory elements including enhancers, silencers and insulators etc. The massively parallel reporter assay (MPRA) methods like STARR-seq facilitate the systematic study of DNA sequence intrinsic enhancer activities in a large scale. However, when applied to human cells, it remains challenging to identify and quantify cell type-specific active enhancers in the genome-wide scale with high-resolution, due to the large size of human genome. In this study, we selected the H3K4me1 associated dinucleosome with the linker DNA sequences as candidate enhancer sequences in two different human cell lines and performed ChIP-STARR-seq to quantify the cell type-specific enhancer activities with high-resolution in a genome-wide scale. Furthermore, we investigated how the activity landscape of enhancer repository would change when transferred from native cells (cis activity) to another cell lines (trans activity). Using ChIP-STARR-seq of the candidate enhancers in native cells and another type of cells, we obtained enhancers cis activity maps and trans activity maps in two different cell lines. The cis and trans activity maps enabled us to identify cell type-specific active enhancers, with enrichment of motifs of differentially expressed TFs. Comparisons between the cis and trans activity maps revealed general consistent regulatory property with different levels of activity in the two cell types, suggesting the sequence intrinsic regulatory properties keep similar in different type of cells. This study provides a new perspective of sequence intrinsic enhancer activities in different types of cells.
Project description:STARR-seq enhancer activity determined following hydrodynamic delivery of STARR-seq plasmid library to mouse liver using three different STARR-seq promoters: Super Core promoter, ORI promoter, and minimal Albumin promoter [G173]
Project description:Long-range activation is an essential property of enhancers, yet the features determining long-range enhancer activities have not been systematically investigated due to a lack of high-throughput methods to measure long-range enhancer activities efficiently. To address this gap, we present a long-range massively parallel reporter assay (long-range MPRA), a genome-integrated assay allowing the measurement of hundreds of enhancers at multiple distances away from a promoter in parallel. The long-range MPRA assay features two independent landing pads, which allow for modular control over the genome-integrated promoter and enhancer libraries. We showcased the capability of long-range MPRA by testing over 300 K562 enhancers, as well as a set of enhancer combinations, at distances up to 100kb. We found that enhancers’ long-range activities are primarily determined by their intrinsic strength, with strong enhancers retaining more activity over long distances, while weak enhancers rapidly lose activity. Additionally, we found that GATA1-bound enhancers are more resistant to distance-dependent loss of activity, suggesting that TF binding also modulates long-range function. Finally, testing long-range enhancer activities with three different promoters (HBE, HBG and GAPDH) revealed that long-range E-P interactions rely on not only enhancer properties but also promoter responsiveness.
Project description:Enhancers play important roles in evolution and disease. However, traditional assays to test enhancers are low throughput and not scalable to the >100,000 enhancers in the human genome. To better prioritize variants associated with disease and to study the role of enhancers, our group and others developed massively parallel reporter assays (MPRAs), which functionally screen thousands of sequences for regulatory activity in parallel. Although MPRAs have been applied to address diverse questions in gene regulation, there has been no systematic comparison of how differences in experimental design influence findings, making it difficult to interpret results and compare between groups. Here, we screen a library of 2,440 sequences, representing candidate liver enhancers and controls, in HepG2 cells for regulatory activity using nine different approaches (including conventional episomal, STARR-seq, and lentiviral MPRA designs). We identify subtle but significant differences in the resulting measurements that correlate with epigenetic and sequence-level features. We also test this library in both orientations with respect to the promoter, validating en masse that enhancer activity is robustly independent of orientation. Finally, we develop and apply a novel method to assemble and functionally test libraries of the same putative enhancers as 192-mers, 354-mers, and 678-mers, and observe surprisingly large differences in functional activity. This work provides a framework for the experimental design of high-throughput reporter assays, suggesting that the extended sequence context of tested elements, and to a lesser degree the precise assay, influence MPRA results.
Project description:We employ a massively parallel reporter assay (MPRA) to measure the ex vivo activities of hundreds of K562 and HepG2 enhancers with known transcription factor motif instances. For seven selected motifs that correspond to known or predicted activators and repressors in the two cell types, we make directed modifications of the bases corresponding to these motifs and observe the changes in enhancer activity. Reporter mRNA-seq from HepG2 and K562 cells transfected with a ~55,000-plex MPRA plasmid pool containing 5,418 mutated human enhancer sequences, each linked to 10 distinct 10-nt tags. The reporter mRNA tags facilitate quantitation of their abundances. The same tags were also sequenced from the transfected MPRA plasmid pool to facilitate normalization to plasmid copy numbers.
Project description:Genomic enhancers are important regulators of gene expression, but their identification is a challenge and methods depend on indirect measures of activity. We developed a method termed STARR-seq to directly and quantitatively assess enhancer activity for millions of candidates from arbitrary sources of DNA, enabling screens across entire genomes. When applied to the Drosophila genome, STARR-seq identifies thousands of cell type-specific enhancers across a broad continuum of strengths, linking differential gene expression to differences in enhancer activity and creating a genome-wide quantitative enhancer map. This map reveals the highly complex regulation of transcription, with several independent enhancers for both developmental regulators and ubiquitously expressed genes. STARR-seq can be used to identify and quantitate enhancer activity in other eukaryotes, including human.