Modulating chromatin accessibility by transactivation and targeting proximal dsgRNAs enhances Cas9 editing efficiency in vivo.
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ABSTRACT:
SUBMITTER: Liu G
PROVIDER: S-EPMC6660936 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:CRISPR-Cas9 technology is routinely applied for targeted mutagenesis in model organisms and cell lines. Recent studies indicate that the prokaryotic CRISPR-Cas9 system is affected by eukaryotic chromatin structures. Here, we show that the likelihood of successful mutagenesis correlates with transcript levels during early development in zebrafish (Danio rerio) embryos. In an experimental setting, we found that guide RNAs differ in their onset of mutagenesis activity in vivo. Furthermore, some guide RNAs with high in vitro activity possessed poor mutagenesis activity in vivo, suggesting the presence of factors that limit the mutagenesis in vivo. Using open access datasets generated from early developmental stages of the zebrafish, and guide RNAs selected from the CRISPRz database, we provide further evidence for an association between gene expression during early development and the success of CRISPR-Cas9 mutagenesis in zebrafish embryos. In order to further inspect the effect of chromatin on CRISPR-Cas9 mutagenesis, we analysed the relationship of selected chromatin features on CRISPR-Cas9 mutagenesis efficiency using publicly available data from zebrafish embryos. We found a correlation between chromatin openness and the efficiency of CRISPR-Cas9 mutagenesis. These results indicate that CRISPR-Cas9 mutagenesis is influenced by chromatin accessibility in zebrafish embryos.
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Project description:Genome editing using CRISPR-associated technology is widely used to modify the genomes rapidly and efficiently on specific DNA double-strand breaks (DSBs) induced by Cas9 endonuclease. However, despite swift advance in Cas9 engineering, structural basis of Cas9-recognition and cleavage complex remains unclear. Proper assembly of this complex correlates to effective Cas9 activity, leading to high efficacy of genome editing events. Here, we develop a CRISPR/Cas9-RAD51 plasmid constitutively expressing RAD51, which can bind to singlestranded DNA for DSB repair. We show that the efficiency of CRISPR-mediated genome editing can be significantly improved by expressing RAD51, responsible for DSB repair via homologous recombination (HR), in both gene knock-out and knock-in processes. In cells with CRISPR/Cas9-RAD51 plasmid, expression of the target genes (cohesin SMC3 and GAPDH) was reduced by more than 1.9-fold compared to the CRISPR/Cas9 plasmid for knock-out of genes. Furthermore, CRISPR/Cas9-RAD51 enhanced the knock-in efficiency of DsRed donor DNA. Thus, the CRISPR/Cas9-RAD51 system is useful for applications requiring precise and efficient genome edits not accessible to HR-deficient cell genome editing and for developing CRISPR/Cas9-mediated knockout technology. [BMB Reports 2023; 56(2): 102-107].
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Project description:CRISPR-Cas9 loss of function (LOF) and base editing screens are powerful tools in genetics and genomics. Yeast is one of the main models in these fields, but has only recently started to adopt this new toolkit for high throughput experiments. We developed a double selection strategy based on co-selection that increases LOF mutation rates using the Target-AID base editor. We constructed the pDYSCKO vector, which is amenable to high throughput double selection experiments, and show that the improvement in Target-AID efficiency generalizes across loci. Using modeling, we show that this improvement in efficiency provides the required increased in detection power to measure the fitness effects of thousands of mutations in typical yeast pooled screens. We show that double selection can also improve Cas9 mediated LOF rates, but that this multiplex genome editing causes programmable chromosomal translocations at high frequency. This suggests that multiplex LOF editing should be performed with caution and that base-editors could be preferable tools for some screens in yeast. Base editing using double selection is simple and straightforward and provides an alternative to homology directed repair based high throughput variant strain construction methods.
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Project description:MotivationThe development of clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has provided a simple yet powerful system for targeted genome editing. In recent years, this system has been widely used for various gene editing applications. The CRISPR editing efficacy is mainly dependent on the single guide RNA (sgRNA), which guides Cas9 for genome cleavage. While there have been multiple attempts at improving sgRNA design, there is a pressing need for greater sgRNA potency and generalizability across various experimental conditions.ResultsWe employed a unique plasmid library expressed in human cells to quantify the potency of thousands of CRISPR/Cas9 sgRNAs. Differential sequence and structural features among the most and least potent sgRNAs were then used to train a machine learning algorithm for assay design. Comparative analysis indicates that our new algorithm outperforms existing CRISPR/Cas9 sgRNA design tools.Availability and implementationThe new sgRNA design tool is freely accessible as a web application, http://crispr.wustl.edu.Supplementary informationSupplementary data are available at Bioinformatics online.
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Project description:CRISPR-associated (Cas) enzymes have revolutionized biology by enabling RNA-guided genome editing. Homology-directed repair (HDR) in the presence of donor templates is currently the most versatile method to introduce precise edits following CRISPR-Cas-induced double-stranded DNA cuts, but HDR efficiency is generally low relative to end-joining pathways that lead to insertions and deletions (indels). We tested the hypothesis that HDR could be increased using a Cas9 construct fused to PRDM9, a chromatin remodeling factor that deposits histone methylations H3K36me3 and H3K4me3 to mediate homologous recombination in human cells. Our results show that the fusion protein contacts chromatin specifically at the Cas9 cut site in the genome to increase the observed HDR efficiency by threefold and HDR:indel ratio by fivefold compared with that induced by unmodified Cas9. HDR enhancement occurred in multiple cell lines with no increase in off-target genome editing. These findings underscore the importance of chromatin features for the balance between DNA repair mechanisms during CRISPR-Cas genome editing and provide a strategy to increase HDR efficiency.
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Project description:The RNA-guided endonuclease Cas9 has emerged as a versatile genome-editing platform. However, the size of the commonly used Cas9 from Streptococcus pyogenes (SpCas9) limits its utility for basic research and therapeutic applications that use the highly versatile adeno-associated virus (AAV) delivery vehicle. Here, we characterize six smaller Cas9 orthologues and show that Cas9 from Staphylococcus aureus (SaCas9) can edit the genome with efficiencies similar to those of SpCas9, while being more than 1 kilobase shorter. We packaged SaCas9 and its single guide RNA expression cassette into a single AAV vector and targeted the cholesterol regulatory gene Pcsk9 in the mouse liver. Within one week of injection, we observed >40% gene modification, accompanied by significant reductions in serum Pcsk9 and total cholesterol levels. We further assess the genome-wide targeting specificity of SaCas9 and SpCas9 using BLESS, and demonstrate that SaCas9-mediated in vivo genome editing has the potential to be efficient and specific.
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Project description:CRISPR-Cas9-based genome editing enables the rapid genetic manipulation of any genomic locus without the need for gene targeting by homologous recombination. Here we describe a conditional transgenic approach that allows temporal control of CRISPR-Cas9 activity for inducible genome editing in adult mice. We show that doxycycline-regulated Cas9 induction enables widespread gene disruption in multiple tissues and that limiting the duration of Cas9 expression or using a Cas9(D10A) (Cas9n) variant can regulate the frequency and size of target gene modifications, respectively. Further, we show that this inducible CRISPR (iCRISPR) system can be used effectively to create biallelic mutation in multiple target loci and, thus, provides a flexible and fast platform to study loss-of-function phenotypes in vivo.
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Project description:The Cas9 endonuclease can be programmed by guide RNA to introduce sequence-specific breaks in genomic DNA. Thus, Cas9-based approaches present a range of novel options for genome manipulation and precision editing. African trypanosomes are parasites that cause lethal human and animal diseases. They also serve as models for studies on eukaryotic biology, including 'divergent' biology. Genome modification, exploiting the native homologous recombination machinery, has been important for studies on trypanosomes but often requires multiple rounds of transfection using selectable markers that integrate at low efficiency. We report a system for delivering tetracycline inducible Cas9 and guide RNA to Trypanosoma brucei. In these cells, targeted DNA cleavage and gene disruption can be achieved at close to 100% efficiency without further selection. Disruption of aquaglyceroporin (AQP2) or amino acid transporter genes confers resistance to the clinical drugs pentamidine or eflornithine, respectively, providing simple and robust assays for editing efficiency. We also use the new system for homology-directed, precision base editing; a single-stranded oligodeoxyribonucleotide repair template was delivered to introduce a single AQP2 - T791G/L264R mutation in this case. The technology we describe now enables a range of novel programmed genome-editing approaches in T. brucei that would benefit from temporal control, high-efficiency and precision.
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