ABSTRACT: We introduce the Multiplexed Editing Regulatory Assay (MERA), a high-throughput CRISPR/Cas9-based approach that analyzes the regulatory genome for function in its native context. By tiling thousands of mutations across ~40 kb of cis-regulatory genomic space and using knock-in GFP reporters to read out gene activity, we obtain quantitative information on the contribution of cis-regulatory regions to gene expression. In addition, we performed a deep-sequencing strategy to find basepair-resolution functional motifs involved in regulation of the gene by sequencing thousands of functional and non-functional genotypes at genomic locations perturbed by specific guide RNAs.
Project description:We introduce the Multiplexed Editing Regulatory Assay (MERA), a high-throughput CRISPR/Cas9-based approach that analyzes the regulatory genome for function in its native context. By tiling thousands of mutations across ~40 kb of cis-regulatory genomic space and using knock-in GFP reporters to read out gene activity, we obtain quantitative information on the contribution of cis-regulatory regions to gene expression. In addition, we performed a deep-sequencing strategy to find basepair-resolution functional motifs involved in regulation of the gene by sequencing thousands of functional and non-functional genotypes at genomic locations perturbed by specific guide RNAs. Design of 3908 gRNAs to perturb regulatory regions associated with the genes Tdgf1,Nanog,Zfp42 and Rpp25 as well as 10 GFP-targetting positive controls. Also, deep-sequencing of genomic regions mutated by 6 selected gRNAs after sorting the electroporated cells into GFP-positive and GFP-negative populations.
Project description:Multiplexed assays of variant effect are powerful methods to profile the consequences of rare variants on gene expression and organismal fitness. Yet, few studies have integrated several multiplexed assays to map variant effects on gene expression in coding sequences. Here, we pioneered a multiplexed assay based on polysome profiling to measure variant effects on translation at scale, uncovering single-nucleotide variants that increase and decrease ribosome load. By combining high-throughput ribosome load data with multiplexed mRNA and protein abundance readouts, we mapped the cis-regulatory landscape of thousands of catechol-O-methyltransferase (COMT) variants from RNA to protein and found numerous coding variants that alter COMT expression. Finally, we trained machine learning models to map signatures of variant effects on COMT gene expression and uncovered both directional and divergent impacts across expression layers. Our analyses reveal expression phenotypes for thousands of variants in COMT and highlight variant effects on both single and multiple layers of expression. Our findings prompt future studies that integrate several multiplexed assays for the readout of gene expression
Project description:Reporter genes integrated into the genome are a powerful tool to reveal effects of regulatory elements and local chromatin context on gene expression. However, so far such reporter assays have been of low throughput. Here we describe a multiplexing approach for the parallel monitoring of transcriptional activity of thousands of randomly integrated reporters. More than 27,000 distinct reporter integrations in mouse embryonic stem cells, obtained with two different promoters, show ~1,000-fold variation in expression levels. Data analysis indicates that lamina-associated domains act as attenuators of transcription, likely by reducing access of transcription factors to binding sites. Furthermore, chromatin compaction is predictive of reporter activity. We also found evidence for cross-talk between neighboring genes, and estimate that enhancers can influence gene expression on average over ~20 kb. The multiplexed reporter assay is highly flexible in design and can be modified to query a wide range of aspects of gene regulation. TRIP assay of mPGK promoter; 6 experiments, each with 2 technical replicates.
Project description:Reporter genes integrated into the genome are a powerful tool to reveal effects of regulatory elements and local chromatin context on gene expression. However, so far such reporter assays have been of low throughput. Here we describe a multiplexing approach for the parallel monitoring of transcriptional activity of thousands of randomly integrated reporters. More than 27,000 distinct reporter integrations in mouse embryonic stem cells, obtained with two different promoters, show ~1,000-fold variation in expression levels. Data analysis indicates that lamina-associated domains act as attenuators of transcription, likely by reducing access of transcription factors to binding sites. Furthermore, chromatin compaction is predictive of reporter activity. We also found evidence for cross-talk between neighboring genes, and estimate that enhancers can influence gene expression on average over ~20 kb. The multiplexed reporter assay is highly flexible in design and can be modified to query a wide range of aspects of gene regulation. TRIP assay of mPGK promotor; 11 clonal cell lines, 1 replicate each
Project description:Post-transcriptional regulation is crucial to shape gene expression. During the Maternal-to-Zygotic transition (MZT), thousands of maternal transcripts are regulated upon fertili-zation and genome activation. Transcript stability can be influenced by cis-elements and trans-factors, but how these inputs are integrated to determine the overall mRNA stability is unclear. Here, we show that most transcripts are under combinatorial regulation by multiple decay pathways. Characterization of the cis-regulatory motifs revealed that nu-cleotide composition bias characteristic of 3’-UTRs poly-U is associated with mRNA stability. In contrast, miR-430, CCUC, CUGC, elements appeared as the main destabiliz-ing motifs, with miR-430 and UAUUUAU (ARE) sequences causing mRNA deadenyla-tion depending on the activation of the genome. We comprehensively identify RNA-protein interactions across the transcriptome during MZT, and their associated regulatory activity. We find that poly-U binding proteins are preferentially associated with 3’-UTR sequences and stabilizing motifs. Analysis of differentially regulated regions revealed antagonistic sequence contexts for poly-C and poly-U binding proteins that shape protein binding and magnitude of regulation across the transcriptome. Finally, we integrate these regulatory motifs into a machine learning model, able to predict the stability of mRNA reporters in vivo. Our findings reveal how mechanisms of post-transcriptional regulation are coordinated to direct changes in mRNA stability within the early embryo.
Project description:We applied a multiplexed genomic tethering assay (Brueckner, Epigenetics Chromatin, 2016; PMID:27777628) to elucidate the function of ACF1, the large subunit of the ACF nucleosome sliding complex in drosophila Kc167 cells. Targeting a Gal4DBD-ACF1 fusion to several hundred integrated reporters revealed a context-dependent repressive effect which is modulated by gene activity and chromatin state.
Project description:Reporter genes integrated into the genome are a powerful tool to reveal effects of regulatory elements and local chromatin context on gene expression. However, so far such reporter assays have been of low throughput. Here we describe a multiplexing approach for the parallel monitoring of transcriptional activity of thousands of randomly integrated reporters. More than 27,000 distinct reporter integrations in mouse embryonic stem cells, obtained with two different promoters, show ~1,000-fold variation in expression levels. Data analysis indicates that lamina-associated domains act as attenuators of transcription, likely by reducing access of transcription factors to binding sites. Furthermore, chromatin compaction is predictive of reporter activity. We also found evidence for cross-talk between neighboring genes, and estimate that enhancers can influence gene expression on average over ~20 kb. The multiplexed reporter assay is highly flexible in design and can be modified to query a wide range of aspects of gene regulation. mRNA profiles of 11 mouse embryonic cell lines each harboring multiple barcoded reporter constructs with mouse PGK promoter integrated at random positions in the genome, single replicate.
Project description:Reporter genes integrated into the genome are a powerful tool to reveal effects of regulatory elements and local chromatin context on gene expression. However, so far such reporter assays have been of low throughput. Here we describe a multiplexing approach for the parallel monitoring of transcriptional activity of thousands of randomly integrated reporters. More than 27,000 distinct reporter integrations in mouse embryonic stem cells, obtained with two different promoters, show ~1,000-fold variation in expression levels. Data analysis indicates that lamina-associated domains act as attenuators of transcription, likely by reducing access of transcription factors to binding sites. Furthermore, chromatin compaction is predictive of reporter activity. We also found evidence for cross-talk between neighboring genes, and estimate that enhancers can influence gene expression on average over ~20 kb. The multiplexed reporter assay is highly flexible in design and can be modified to query a wide range of aspects of gene regulation. TRIP assay of tet-Off promotor; 4 experiments, each with 2 technical replicates. Each experiment was induced at 4 different concentrations of doxycycline.
Project description:Most mammalian genes have multiple polyA sites, representing a substantial source of transcript diversity regulated by the cleavage and polyadenylation (CPA) machinery. To better understand how these proteins govern polyA site choice we introduce CPA-Perturb-seq, a multiplexed perturbation screen dataset of 42 CPA regulators with a 3’ scRNA-seq readout that enables transcriptome-wide inference of polyA site usage. We develop a framework to detect perturbation-dependent changes in polyadenylation and characterize modules of co-regulated polyA sites. We find groups of intronic polyA sites regulated by distinct components of the nuclear RNA life cycle including elongation, splicing, termination, and surveillance. We train and validate a multi-task deep neural network (APARENT-Perturb) for tandem polyA site usage, delineating a cis-regulatory code that predicts perturbation response and reveals interactions between regulatory complexes. Our work highlights the potential for multiplexed single-cell perturbation screens to further our understanding of post-transcriptional regulation.
Project description:Most mammalian genes have multiple polyA sites, representing a substantial source of transcript diversity regulated by the cleavage and polyadenylation (CPA) machinery. To better understand how these proteins govern polyA site choice we introduce CPA-Perturb-seq, a multiplexed perturbation screen dataset of 42 CPA regulators with a 3’ scRNA-seq readout that enables transcriptome-wide inference of polyA site usage. We develop a framework to detect perturbation-dependent changes in polyadenylation and characterize modules of co-regulated polyA sites. We find groups of intronic polyA sites regulated by distinct components of the nuclear RNA life cycle including elongation, splicing, termination, and surveillance. We train and validate a multi-task deep neural network (APARENT-Perturb) for tandem polyA site usage, delineating a cis-regulatory code that predicts perturbation response and reveals interactions between regulatory complexes. Our work highlights the potential for multiplexed single-cell perturbation screens to further our understanding of post-transcriptional regulation.