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:We combined Self-Transcribing Active Regulatory Region Sequencing (STARR-seq) with an enrichment step using chromatin immunoprecipitation in a massively parallel reporter assay. We applied this assay, termed ChIP-STARR-seq, to normal (primed) and naive human embryonic stem cells, building up a comprehensive catalogue of functional enhancers. This database record describes the DNA-seq component from plasmid libraries prior to transfection.
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:We performed an original protocol called synthetic STARR-seq (PMID: 30427832) in which a library of putative response elements are tested for their capacity to bind thyroid hormone (T3) nuclear receptors and convey T3 transactivation More than 10 000 putative T3 response elements (T3RE) were cloned in the hSTARR-seq-ORI vector with a minimal promoter, in the 3' end of the transcribed sequence. These are variant of the consensus T3RE (5'NGGTCANNNNRGGNNA3') Therefore the most active T3RE are over-represented in the RNA of cells transfected with the plasmid library and treated with T3.
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:Enhancers are distal regulators of gene expression that shape cell identity and regulate cell fate transitions. Mouse embryonic stem cells (mESCs) are a typical example of cells whose pluripotent identity is maintained by a complex enhancer landscape, that is drastically altered upon differentiation. Genome-wide chromatin accessibility and histone modification assays are commonly used as a proxy for enhancer location, strength and dynamics. Here, we applied STARR-seq, a genome-wide plasmid-based assay, to measure the enhancer potential of genomic loci in a plasmid context in “ground-state” (2i+LIF; 2iL-ESCs) and “metastable” (serum+LIF; SL-ESCs) embryonic stem cells.
Project description:Massively parallel reporter assays (MPRAs) test the capacity of putative gene regulatory elements to drive transcription on a genome-wide scale. Most gene regulatory activity occurs within accessible chromatin, and recently described methods have combined assays that capture these regions—such as assay for transposase-accessible chromatin using sequencing (ATAC-seq)—with self-transcribing active regulatory region sequencing (STARR-seq) to selectively assay the regulatory potential of accessible DNA (ATAC-STARR-seq). Here, we report an integrated approach that quantifies activating and silencing regulatory activity, chromatin accessibility, and transcription factor (TF) occupancy with one assay using ATAC-STARR-seq. Our strategy, including important updates to the ATAC-STARR-seq assay and workflow, enabled high-resolution testing of ~50 million unique DNA fragments tiling ~101,000 accessible chromatin regions in human lymphoblastoid cells. We discovered that 30% of all accessible regions contain an activator, a silencer or both. Although few MPRA studies have explored silencing activity, we demonstrate silencers occur at similar frequencies to activators, and they represent a distinct functional group enriched for unique TF motifs and repressive histone modifications. We further show that Tn5 cut-site frequencies are retained in the ATAC-STARR plasmid library compared to standard ATAC-seq, enabling TF occupancy to be ascertained from ATAC-STARR data. With this approach, we found that activators and silencers cluster by distinct TF footprint combinations and these groups of activity represent different gene regulatory networks of immune cell function. Altogether, these data highlight the multi-layered capabilities of ATAC-STARR-seq to comprehensively investigate the regulatory landscape of the human genome all from a single DNA fragment source.