Substantial collateral effects induced by CasRx in mammalian cells and mice
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE157586 | GEO | 2025/09/02
REPOSITORIES: GEO
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Project description:The CRISPR/Cas13 system has garnered attention as a potential tool for RNA editing. However, the degree of collateral activity among various Cas13 orthologs and their cytotoxic effects in mammalian cells remain contentious, potentially impacting their applications. In this study, we observed differential collateral activities for LwaCas13a and RfxCas13d in 293T and U87 cells by applying both sensitive dual-fluorescence (mRuby/GFP) reporter and quantifiable dual-luciferase (Fluc/Rluc) reporter, with LwaCas13a displaying notable activity contrary to previous reports. However, significant collateral RNA cleavage exerted only a modest impact on cell viability. Furthermore, the collateral activity of LwaCas13a mildly impeded but did not arrest, porcine embryo development. Our findings reveal that distinct collateral RNA cleavage by Cas13 slightly suppresses mammalian cell proliferation and embryo development. This could account for the lack of reported collateral effects in numerous prior studies and offers new insights into the implications of the collateral activity of Cas13 for clinical application.
2024-01-25 | GSE254168 | GEO
Project description:CRISPR-Cas13 systems have been adapted as versatile toolkits for RNA-related applications. Here we systematically evaluate the performance of several prominent Cas13 family effectors (Cas13a, Cas13b and Cas13d) under lentiviral vectors and reveal surprisingly differential defects and characteristics of these systems. Using RNA immunoprecipitation sequencing, transcriptome profiling, biochemistry analysis and high-throughput CRISPR-Cas13 screening approaches, we determine that each Cas13 system has its intrinsic RNA targets in mammalian cells. Viral process-related host genes can be targeted by Cas13 and affect the production of fertile lentiviral particles, thereby restricting the utility of lentiviral Cas13 systems. Multiple RNase activities of Cas13 are involved in endogenous RNA targeting. Unlike target-induced collateral effect, intrinsic RNA targeting can be specific, target-independent and dynamically tuned by varied states of Cas13 nucleases. Our work not only provides guidance to appropriately utilize lentiviral Cas13 systems, but also raises cautions about intrinsic RNA targeting during Cas13-based basic and therapeutic applications.
2023-10-09 | GSE202841 | GEO
Project description:CRISPR-Cas13 systems have been adapted as versatile toolkits for RNA-related applications. Here we systematically evaluate the performance of several prominent Cas13 family effectors (Cas13a, Cas13b and Cas13d) under lentiviral vectors and reveal surprisingly differential defects and characteristics of these systems. Using RNA immunoprecipitation sequencing, transcriptome profiling, biochemistry analysis and high-throughput CRISPR-Cas13 screening approaches, we determine that each Cas13 system has its intrinsic RNA targets in mammalian cells. Viral process-related host genes can be targeted by Cas13 and affect the production of fertile lentiviral particles, thereby restricting the utility of lentiviral Cas13 systems. Multiple RNase activities of Cas13 are involved in endogenous RNA targeting. Unlike target-induced collateral effect, intrinsic RNA targeting can be specific, target-independent and dynamically tuned by varied states of Cas13 nucleases. Our work not only provides guidance to appropriately utilize lentiviral Cas13 systems, but also raises cautions about intrinsic RNA targeting during Cas13-based basic and therapeutic applications.
2023-10-09 | GSE202838 | GEO
Project description:CRISPR-Cas13 systems have been adapted as versatile toolkits for RNA-related applications. Here we systematically evaluate the performance of several prominent Cas13 family effectors (Cas13a, Cas13b and Cas13d) under lentiviral vectors and reveal surprisingly differential defects and characteristics of these systems. Using RNA immunoprecipitation sequencing, transcriptome profiling, biochemistry analysis and high-throughput CRISPR-Cas13 screening approaches, we determine that each Cas13 system has its intrinsic RNA targets in mammalian cells. Viral process-related host genes can be targeted by Cas13 and affect the production of fertile lentiviral particles, thereby restricting the utility of lentiviral Cas13 systems. Multiple RNase activities of Cas13 are involved in endogenous RNA targeting. Unlike target-induced collateral effect, intrinsic RNA targeting can be specific, target-independent and dynamically tuned by varied states of Cas13 nucleases. Our work not only provides guidance to appropriately utilize lentiviral Cas13 systems, but also raises cautions about intrinsic RNA targeting during Cas13-based basic and therapeutic applications.
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Project description:Cas13 is a unique family of CRISPR endonucleases exhibiting programmable binding and cleavage of RNAs and is a strong candidate for eukaryotic RNA knockdown in the laboratory and the clinic. However, sequence-specific binding of Cas13 to the target RNA unleashes non-specific bystander RNA cleavage, or collateral activity, which may confound knockdown experiments and raises concerns for therapeutic applications. Although conserved across orthologs and robust in cell-free and bacterial environments, the extent of collateral activity in mammalian cells remains disputed. Here, we investigate Cas13d collateral activity in the context of an RNA-targeting therapy for myotonic dystrophy type 1, a disease caused by a transcribed long CTG repeat expansion. We find that when targeting CUGn RNA in HeLa and other cell lines, Cas13d depletes endogenous and transgenic RNAs, interferes with critical cellular processes, and activates stress response and apoptosis pathways. We also observe collateral effects when targeting other repetitive and unique transgenic sequences, and we provide evidence for collateral activity when targeting highly expressed endogenous transcripts. To minimize collateral activity for repeat-targeting Cas13d therapeutics, we introduce gRNA excision for negative-autoregulatory optimization (GENO), a simple strategy that leverages crRNA processing to control Cas13d expression and is easily integrated into an AAV gene therapy. We argue that thorough assessment of collateral activity is necessary when applying Cas13d in mammalian cells and that implementation of GENO illustrates the advantages of compact and universally robust regulatory systems for Cas-based gene therapies.
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Project description:We found that several variants with 2-4 mutations on Higher Eukaryotes and Prokaryotes Nucleotide-binding (HEPN) domains showed undiminished on-target activity but markedly reduced collateral effects. Furthermore, transcriptome-wide off-target effects and cell growth arrest induced by wild-type Cas13d were found to be absent for a Cas13d variant. Thus, high-fidelity Cas13 variants with minimal collateral effects are now available for the targeted degradation of RNAs in basic research and therapeutic applications.
2022-06-28 | GSE168246 | GEO
Project description:The possibility of collateral RNA degradation poses a concern for transcriptome perturbations and therapeutic applications using CRISPR-Cas13. We show that collateral activity only occurs with high RfxCas13d expression. Using low-copy RfxCas13d in transcriptome-scale and combinatorial pooled screens, we achieve high on-target knockdown without extensive collateral activity. Further, analysis of a high-fidelity Cas13 variant suggests that its reduced collateral activity may be due to overall diminished nuclease capability.
2024-12-18 | GSE284017 | GEO
Project description:The intrinsic collateral cleavage activity of Cas13d,which refers to the gRNA-independent degradation of bystander RNA, significantly limits its therapeutic potential. To extensively evaluate the collateral effects of hpCas13d genome-wide, we conducted RNA-seq analysis of the transcriptome in HEK293T cells after the transfections with dCas13d, wtCas13d, hpCas13d, and hfCas13d . Compared to dCas13d, wtCas13d with a PPIA gRNA (reported to induce the significant collateral cleavage) resulted in significant downregulations of thousands genes. In sharp contrast, hpCas13d and hfCas13d showed much less off-target genes, respectively. These findings demonstrate that hpCas13d exhibits reduced collateral activity, rendering it suitable for in vivo applications.
2024-02-28 | GSE260500 | GEO
Project description:Transient elimination of RNAs by CRISPR-Cas13 systems has been widely used in basic and applied sciences over the last years. However, the efficiency of the system can be enhanced in vivo, and its application has generated controversy due to the recently described collateral activity in mammalian cells and mouse models. Here, we have optimized the CRISPR-RfxCas13d (CasRx) system for an optimized RNA targeting in vivo in zebrafish embryos, by different and compatible approaches. These strategies include the use of chemically modified guide RNAs to increase and sustain mRNA knockdown, an improved nuclear targeting, and the evaluation of ex vivo computational models for predicting gRNA efficiency in vivo. Furthermore, our study demonstrated that transient CRISPR-RfxCas13d approaches can effectively deplete endogenous mRNAs in zebrafish embryos without inducing collateral effects, except for targeting extremely abundant RNAs. For that, we have implemented alternative RNA-targeting CRISPR-Cas systems with reduced or absent collateral activity in zebrafish embryos. Altogether, these findings contribute to optimize CRISPR-Cas technology for RNA targeting in zebrafish through transient approaches and assist the progress of potential implications for knockdown therapies in vivo.
2025-01-22 | GSE284120 | GEO
Project description:Transient elimination of RNAs by CRISPR-Cas13 systems has been widely used in basic and applied sciences over the last years. However, the efficiency of the system can be enhanced in vivo, and its application has generated controversy due to the recently described collateral activity in mammalian cells and mouse models. Here, we have optimized the CRISPR-RfxCas13d (CasRx) system for an optimized RNA targeting in vivo in zebrafish embryos, by different and compatible approaches. These strategies include the use of chemically modified guide RNAs to increase and sustain mRNA knockdown, an improved nuclear targeting, and the evaluation of ex vivo computational models for predicting gRNA efficiency in vivo. Furthermore, our study demonstrated that transient CRISPR-RfxCas13d approaches can effectively deplete endogenous mRNAs in zebrafish embryos without inducing collateral effects, except for targeting extremely abundant RNAs. For that, we have implemented alternative RNA-targeting CRISPR-Cas systems with reduced or absent collateral activity in zebrafish embryos. Altogether, these findings contribute to optimize CRISPR-Cas technology for RNA targeting in zebrafish through transient approaches and assist the progress of potential implications for knockdown therapies in vivo.
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