Mapping and dissecting essential regulatory elements using multi-resolution CRISPR screens
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PROVIDER: PRJNA894448 | ENA |
REPOSITORIES: ENA
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Project description:Hundreds of thousands of candidate cis-regulatory elements (cCREs) have been identified across a myriad of cell types, but relatively few have been empirically characterized. Here, we present a scalable, phenotype-driven CRISPR screening method to test thousands of regulatory elements in parallel, by perturbing thousands of DNase hypersensitive sites (DHS) around hundreds of essential genes in K562. Integrating data from Cas9 exon-targeting with our CRISPRi screens, we nominate and validate promoters that regulate other nearby genes. Using higher-resolution CRISPR systems (dCas9 alone or Cas9) to tile across several essential enhancers, we resolve distinct peaks of activity and dissect core transcription factor binding sites (TFBSs) within enhancers, highlighting the advantages of complementary CRISPR systems to investigate CREs. Lastly, we use our tiling results to interrogate how TFBSs interact to drive enhancer function at the CBFA2T3 locus. This study demonstrates a scalable CRISPR screening framework for identifying and dissecting CREs that regulate cellular phenotypes.
2023-01-31 | GSE216577 | GEO
Project description:CRISPR tiling screens have advanced the identification and characterization of regulatory sequences but are limited by low resolution arising from the indirect readout of editing via guide RNA sequencing. This study introduces CRISPR-CLEAR, an end-to-end experimental assay and computational pipeline, which leverages targeted sequencing of CRISPR-introduced alleles at the endogenous target locus following dense base-editing mutagenesis. This approach enables the dissection of regulatory elements at nucleotide resolution, facilitating a direct assessment of genotype-phenotype effects.
2024-10-03 | GSE278581 | GEO
Project description:Pooled CRISPR-Cas9 screens have recently emerged as a powerful method for functionally characterizing regulatory elements in the non-coding genome, but off-target effects in these experiments have not been systematically evaluated. Here, we conducted multiple genome-scale CRISPR screens for essential CTCF loop anchors in the human K562 erythroid cell line. Surprisingly, the primary drivers of apparent ``hits'' in this screen were single guide RNAs (sgRNAs) with low sequence specificity. After removing these confounders, we found that no CTCF loop anchors among the ones we screened are essential for cell growth in culture. We also observed analogous effects in independent non-coding screens densely tiling regulatory elements and genomic neighborhoods near previously known essential genes. Strikingly, we found that low-specificity guides also result in strong confounding growth effects in screens employing epigenetic perturbations that do not cause DNA damage, such as CRISPRi and CRISPRa. Remarkably, the set of confounded guides is distinct for each perturbation mode. Promisingly, strict filtering of CRISPRi libraries using GuideScan-aggregate specificity scores removed these confounded sgRNAs and allowed for the identification of essential enhancers, which we validated extensively. Our stduy presents the first genome-scale functional characterization of CTCF binding sites in the human genome, while also identifying the limitations on and outlining the future prospects for the detailed functional dissection of regulatory elements in the genome using Cas9.
2019-07-01 | GSE131349 | GEO
Project description:Genome-scale pooled CRISPR screens are powerful tools for identifying genetic dependencies across varied cellular processes. The vast majority of CRISPR screens reported to date have focused exclusively on the perturbation of protein-coding gene function. However, protein-coding genes comprise <2% of the sequence space in the human genome leaving a substantial portion of the genome uninterrogated. Noncoding regions of the genome harbor important regulatory elements (e.g. promoters, enhancers, suppressors) that influence cellular processes but high-throughput methods for evaluating their essentiality have yet to be established. Here, we describe a CRISPR-based screening approach that facilitates the functional profiling of thousands of noncoding regulatory elements in parallel. We selected the tumor suppressor p53 as a model system and designed a pooled CRISPR library targeting thousands of p53 binding sites throughout the genome. Following transduction into dCas9-KRAB-expressing cells we identified several regulatory elements that influence cell proliferation. Moreover, we uncovered multiple elements that are required for the p53-mediated DNA damage response. Surprisingly, many of these elements are located deep within intergenic regions of the genome that have no prior functional annotations. This work diversifies the applications for pooled CRISPR screens and provides a framework for future functional studies focused on noncoding regulatory elements.
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Project description:Polycomb-mediated chromatin repression modulates gene expression during development in metazoans. Binding of multiple sequence-specific factors at discrete Polycomb Response Elements (PREs) is thought to recruit repressive complexes that spread across an extended chromatin domain. To dissect the structure of PREs, we applied high-resolution mapping of non-histone chromatin proteins in native chromatin of Drosophila cells. Analysis of occupied sites reveal cooperative interactions between transcription factors that stabilize Polycomb anchoring to DNA, and implicate the general transcription factor Adf1 as a novel PRE component. By comparing two Drosophila cell lines with differential chromatin states, we provide evidence that repression is accomplished at multiple steps in transcription, including inactivation of distant enhancers, enhanced Polycomb recruitment to PREs and target promoters, and elevated stalling of RNAPII in repressed genes. These results suggest that the stability of complexes bridging promoters, enhancers, and PREs is a crucial aspect of developmentally regulated gene expression. Native chromatin immunoprecipitation of histones, transcription factors and Polycomb protein in Drosophila cell lines.
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Project description:The ability to perturb genes in human cells is crucial for elucidating gene function and holds great potential for finding therapeutic targets for diseases such as cancer. To extend the catalog of human core and context- dependent fitness genes, we have developed a high-complexity second-generation genome-scale CRISPR-Cas9 gRNA library and applied it to fitness screens in five human cell lines. Using an improved Bayesian analytical approach, we consistently discover 5-fold more fitness genes than were previously observed. We present a list of 1,580 human core fitness genes and describe their general properties. Moreover, we demonstrate that context-dependent fitness genes accurately recapitulate pathway-specific genetic vulnerabilities induced by known oncogenes and reveal cell-type-specific dependencies for specific receptor tyrosine kinases, even in oncogenic KRAS backgrounds. Thus, rigorous identification of human cell line fitness genes using a high-complexity CRISPR-Cas9 library affords a high-resolution view of the genetic vulnerabilities of a cell. Additional data can be found at tko.ccbr.utoronto.ca RNAseq of five human cell lines with Cas9 knock-ins.
2015-11-25 | E-GEOD-75189 | biostudies-arrayexpress
Project description:Polycomb-mediated chromatin repression modulates gene expression during development in metazoans. Binding of multiple sequence-specific factors at discrete Polycomb Response Elements (PREs) is thought to recruit repressive complexes that spread across an extended chromatin domain. To dissect the structure of PREs, we applied high-resolution mapping of non-histone chromatin proteins in native chromatin of Drosophila cells. Analysis of occupied sites reveal cooperative interactions between transcription factors that stabilize Polycomb anchoring to DNA, and implicate the general transcription factor Adf1 as a novel PRE component. By comparing two Drosophila cell lines with differential chromatin states, we provide evidence that repression is accomplished at multiple steps in transcription, including inactivation of distant enhancers, enhanced Polycomb recruitment to PREs and target promoters, and elevated stalling of RNAPII in repressed genes. These results suggest that the stability of complexes bridging promoters, enhancers, and PREs is a crucial aspect of developmentally regulated gene expression.
2014-02-08 | GSE47829 | GEO
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