Negative autoregulation mitigates collateral RNase activity of repeat-targeting CRISPR-Cas13d in mammalian cells
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ABSTRACT:
PROVIDER: PRJNA790986 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR17282645_1.fastq.gz | Fastqsanger.gz | |||
| SRR17282645_2.fastq.gz | Fastqsanger.gz | |||
| SRR17282646_1.fastq.gz | Fastqsanger.gz | |||
| SRR17282646_2.fastq.gz | Fastqsanger.gz | |||
| SRR17282647_1.fastq.gz | Fastqsanger.gz |
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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.
2021-12-23 | GSE191329 | GEO
Project description:CRISPR-Cas13 RNA endonucleases show promise for programmable RNA knockdown. However, sequence-specific binding of Cas13 unleashes non-specific bystander RNA cleavage, or collateral activity, raising concerns for experiments and therapeutic applications. Although robust in cell-free and bacterial environments, collateral activity in mammalian cells remains disputed. We investigate Cas13d collateral activity in a therapeutic context for myotonic dystrophy type 1, caused by a transcribed CTG repeat expansion. We find that, when targeting CUGn RNA in mammalian cells, Cas13d depletes endogenous and transgenic RNAs, interferes with critical cellular processes, and activates stress response and apoptosis. Collateral effects also occur when targeting abundant endogenous transcripts. To minimize collateral activity for repeat-targeting approaches, we introduce GENO, an adeno-associated virus-compatible strategy that leverages guide RNA processing to control Cas13d expression. We argue that thorough assessment of collateral activity is necessary when applying Cas13 in mammalian cells and that GENO illustrates advantages of compact regulatory systems for Cas-based gene therapies.
| S-EPMC9809062 | biostudies-literature
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.
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Project description:transcriptome-wide collateral effects of Cas13d variants
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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.
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Project description:We performed an experimental Cas13d-SARScov2 genome-wide screen to identify gRNAs that would allow Cas13d to degrade the viral RNA. We built mCherry reporter plasmids that express mCherry with a 3kb 3'UTR deriving from the SARScov2 genome. In total we designed 11 reporters covering the entire plus strand of the viral genome and 11 other reporters covering the entire minus strand. Each of the 22 mCherry reporter plasmids carries a U6 expression cassette containing a Cas13d gRNA that targets the 3'UTR of the mCherry reporter. Each reporter is represented by a pool of reporters each containing a different gRNA that targets mCherry 3'UTR for a total average of ~300 gRNA per 3'UTR. The entire pool of 22 reporters, each with a pool of ~300 different gRNAs constitutes a comprehensive set ~6,500 reporters (~ 6,500 different gRNAs) that allowed us to interrogate the entire SARScov2 plus and minus strand viral RNA for regions of vulnerability and targetability. In order to specifically interrogate Cas13d activity an remove the biases that would be introduced in the reporter expression by the presence of a large 3kb 3'UTR we used a case (presence of Cas13d) control (absence of Cas13d) design. Briefly, the ~6,500 reporters were lentiviral transduced in RKO cells, the cells were split in 2 populations, 1 population was transduced with Cas13d and the other serving as control did not. The population expressing Cas13d was FACS sorted in low mCherry (efficient gRNAs) and high mCherry (un-efficient gRNAs) in 2 biological replicates and the genomic DNA of these populations was extracted, gRNAs were PCR amplified and sequenced. For the population that did not express Cas13d, a low mCherry, one high mCherry and unsorted population were sequenced as control libraries.
2023-10-29 | E-MTAB-11111 | biostudies-arrayexpress
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:Endoribonucleases govern the maturation and degradation of RNA and are indispensable in the post-transcriptional regulation of gene expression. A key endoribonuclease in many bacteria is RNase E. To ensure an appropriate supply of RNase E, some bacteria such as E. coli have evolved a tightly functioning feedback regulation of RNase E, which is mediated in cis by the rne 5′-untranslated region (5′UTR); however, the mechanisms involved in the control of RNase E in other bacteria have largely remained unknown. Cyanobacteria rely on solar light as energy source for their photosynthetic lifestyle, despite the inherent ultraviolet (UV) irradiation. Here, we revealed the global gene expression response in the cyanobacterium Synechocystis sp. PCC 6803 after exposure to UV light and discovered a unique response of RNase E: a rapidly increasing enzymatic activity although stability of the protein was lowered . In parallel, we observed a substantial stabilization of the full-length mRNA specifically after UV-C treatment, while the 5′UTR accumulated under all conditions. Mapping of RNA 3′ends and in vitro cleavage assays revealed that RNase E cleaves within a stretch of six consecutive uridine residues within the rne 5′UTR, indicating the autoregulation of RNase E via its own 5′UTR. These observations imply that RNase E in cyanobacteria evolved as a substantial contributor in re-shaping the transcriptome during the UV stress response, that its required activity level is maintained despite enhanced turnover of the protein, and that the underlying mechanism involves a feedback mechanism acting on a uridine-rich element within the rne 5′UTR.
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Project description:Circular RNAs (circRNAs) are widely expressed, but their functions remain largely unknown. To study circRNAs in a high-throughput manner, short hairpin RNA (shRNA) screens1 have recently been used to deplete circRNAs by targeting their unique back-splicing junction (BSJ) sites. Here, we report frequent discrepancies between shRNA-mediated circRNA knockdown efficiency and the corresponding biological effect, raising pressing concerns about the robustness of shRNA screening for circRNA functional characterization. To address this issue, we leveraged the CRISPR/Cas13d system2 for functional study of circRNAs by optimizing the strategy for designing single guide RNAs to deplete circRNAs. We then performed shRNA and CRISPR/Cas13d parallel screenings and demonstrated that shRNA-mediated circRNA screening yielded a high rate of false positive phenotypes. Furthermore, using a CRISPR/Cas13d screening library targeting over 2,500 human hepatocellular carcinomas (HCC) related circRNAs, we identified a group of circRNAs, whose inhibition increased the therapeutic efficacy of sorafenib, an approved HCC drug. Collectively, these data demonstrate that CRISPR/Cas13d system is an effective approach to study the function of circRNAs in a high-throughput manner.
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