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Engineered CRISPR-Cas12a for higher-order combinatorial chromatin perturbations (Nanopore)

ABSTRACT: Multiplexed genetic perturbations are critical for testing functional interactions among coding or non-coding genetic elements. Compared to double-stranded DNA cutting, repressive chromatin formation using CRISPR interference (CRISPRi) avoids genotoxicity and is more effective for perturbing non-coding regulatory elements in pooled assays. However, current CRISPRi pooled screening approaches are limited to targeting 1-3 genomic sites per cell. We engineer an Acidaminococcus Cas12a (AsCas12a) variant, multiplexed transcriptional interference AsCas12a (multiAsCas12a), that incorporates R1226A, a mutation that stabilizes the ribonucleoprotein:DNA complex via DNA nicking. The multiAsCas12a-KRAB fusion improves CRISPRi activity over DNase-dead AsCas12a-KRAB fusions, often rescuing the activities of lentivirally delivered CRISPR RNAs (crRNA) that are inactive when used with the latter. multiAsCas12a-KRAB supports CRISPRi using 6-plex crRNA arrays in high-throughput pooled screens. Using multiAsCas12a-KRAB, we discover enhancer elements and dissect the combinatorial function of cis-regulatory elements in human cells. These results instantiate a group testing framework for efficiently surveying numerous combinations of chromatin perturbations for biological discovery and engineering.

ORGANISM(S): Homo sapiens

PROVIDER: GSE260827 | GEO | 2024/03/06

REPOSITORIES: GEO

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Engineered CRISPR-Cas12a for higher-order combinatorial chromatin perturbations (amplicon)

Project description:Multiplexed genetic perturbations are critical for testing functional interactions among coding or non-coding genetic elements. Compared to double-stranded DNA cutting, repressive chromatin formation using CRISPR interference (CRISPRi) avoids genotoxicity and is more effective for perturbing non-coding regulatory elements in pooled assays. However, current CRISPRi pooled screening approaches are limited to targeting 1-3 genomic sites per cell. We engineer an Acidaminococcus Cas12a (AsCas12a) variant, multiplexed transcriptional interference AsCas12a (multiAsCas12a), that incorporates R1226A, a mutation that stabilizes the ribonucleoprotein:DNA complex via DNA nicking. The multiAsCas12a-KRAB fusion improves CRISPRi activity over DNase-dead AsCas12a-KRAB fusions, often rescuing the activities of lentivirally delivered CRISPR RNAs (crRNA) that are inactive when used with the latter. multiAsCas12a-KRAB supports CRISPRi using 6-plex crRNA arrays in high-throughput pooled screens. Using multiAsCas12a-KRAB, we discover enhancer elements and dissect the combinatorial function of cis-regulatory elements in human cells. These results instantiate a group testing framework for efficiently surveying numerous combinations of chromatin perturbations for biological discovery and engineering.

2024-03-05 | GSE260830 | GEO

Engineered CRISPR-Cas12a for higher-order combinatorial chromatin perturbations (CRISPR screen)

2024-03-06 | GSE260829 | GEO

Engineered CRISPR-Cas12a for higher-order combinatorial chromatin perturbations (RNA-Seq)

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RNA-seq of CSMD1 enhancer CRISPRi in LUHMES cells and differentiated neurons

Project description:we performed lentiviral CRISPR interference (CRISPRi) by recruiting dCas9 fused with the KRAB domain to the CSMD1 enhancer (fam3) in the neuronal precursor cell line – Lund human mesencephalic (LUHMES). Given that the expression of CSMD1 was not detectable in LUHMES cells we differentiated these cells into neurons. Differentiated neurons with CRISPRi of CSMD1 enhancer showed significantly higher expression of CSMD1 than control.

2022-06-30 | E-MTAB-8027 | biostudies-arrayexpress

Processing-Independent CRISPR RNAs Limit Natural Transformation in Neisseria meningitidis

Project description:In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis. dRNA-seq approach for RNA samples from cultures of N. lactamica 020-06, harvested at mid-log. Two cDNA libraries from total RNA were prepared to distinguish between transcripts with either primary orprocessed 5’ ends: one library is generated from untreated RNA, whereas the other is treated with terminator exonuclease (TEX),

2013-04-23 | E-GEOD-44582 | biostudies-arrayexpress

Generation and characterization of inducible KRAB-dCas9 iPSCs from primates for cross-species CRISPRi

Project description:Comparisons of molecular phenotypes across primates provide unique information to understand human biology and evolution and single-cell RNA-seq CRISPR interference screens are a powerful approach to analyze them. Here, we generate and validate three human, three gorilla and two cynomolgus iPS cell lines that carry a dox-inducible KRAB-dCas9 construct in the AAVS1 locus. We show that despite variable expression levels of KRAB-dCas9 among lines, comparable downregulation of target genes and comparable phenotypic effects are observed in a single-cell RNA-seq CRISPR interference screen. Hence, we provide valuable resources for performing and further extending CRISPRi screens in human and non-human primates.

2024-02-20 | GSE255980 | GEO

Generation and characterization of inducible KRAB-dCas9 iPSCs from primates for cross-species CRISPRi

2024-03-26 | GSE241293 | GEO

Identification and mitigation of pervasive off-target activity in CRISPR-Cas9 screens for essential non-coding elements

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

Processing-Independent CRISPR RNAs Limit Natural Transformation in Neisseria meningitidis

2013-04-23 | GSE44582 | GEO

A multiplexed single-cell CRISPR screening platform enables systematic dissection of the unfolded protein response

Project description:Functional genomics efforts face tradeoffs between number of perturbations examined and complexity of phenotypes measured. We bridge this gap with Perturb-seq, which combines droplet-based single-cell RNA-seq with a strategy for barcoding CRISPR-mediated perturbations, allowing many perturbations to be profiled in pooled format. We applied Perturb-seq to dissect the mammalian unfolded protein response (UPR) using single and combinatorial CRISPR perturbations. A genome-scale CRISPR interference (CRISPRi) screen identified genes whose depletion perturbs ER homeostasis. Subjecting ~100 hits to Perturb-seq enabled high-precision functional clustering of genes. Single-cell analyses revealed epistasis among the three UPR branches, bifurcated UPR branch activation between cells subject to the same perturbation, and differential activation of the branches across hits, including a feedback loop between the translocon and the IRE1α branch. These studies provide insight into how the three sensors of ER homeostasis monitor distinct types of stress and highlight the ability of Perturb-seq to dissect complex cellular responses.

2016-12-15 | GSE90546 | GEO

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