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A Cas12a ortholog with stringent PAM recognition followed by low off-target editing rates for genome editing

ABSTRACT: A Cas12a ortholog with stringent PAM recognition followed by low off-target editing rates for genome editing

PROVIDER: PRJNA610555 | ENA |

REPOSITORIES: ENA

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A Cas12a ortholog with stringent PAM recognition followed by low off-target editing rates for genome editing

Project description:Our study shows that CeCas12a nuclease is active in human cells and the stringency of PAM recognition could be an important factor shaping off-target editing in gene editing. Thus, CeCas12a provides a promising candidate with distinctive characteristics for research and therapeutic applications

2020-03-06 | GSE146420 | GEO

Cas12a variants designed for lower genome-wide off-target effect through stringent PAM recognition

Project description:our findings show that the Cas proteins could be designed to be stringent in PAM recognition to reduce their off-target effects , which points out a promising and practical way for the minimization of the off-targeting in genome editing.

2021-10-09 | GSE185486 | GEO

Randomized PAM depletion of phylogenetically-diverse Cas12a nucleases

Project description:We report the PAMs of phylogenetically-diverse Cas12a nucleases using a cell-free TXTL-based PAM screen. By adding a 5N randomized PAM library and Cas12a-gRNA in vitro, recognized PAM sequences were cleaved, while non-recognized PAMs remained. By amplifying the non-cleaved DNA, we used next-generation sequencing to analyze the depletion of functional PAMs of these Cas12a nucleases.

2020-03-02 | GSE130377 | GEO

A Cas12a ortholog with stringent PAM recognition followed by low off-target editing rates for genome editing.

Project description:BackgroundAsCas12a and LbCas12a nucleases are reported to be promising tools for genome engineering with protospacer adjacent motif (PAM) TTTV as the optimal. However, the C-containing PAM (CTTV, TCTV, TTCV, etc.) recognition by Cas12a might induce extra off-target edits at these non-canonical PAM sites.ResultsHere, we identify a novel Cas12a nuclease CeCas12a from Coprococcus eutactus, which is a programmable nuclease with genome-editing efficiencies comparable to AsCas12a and LbCas12a in human cells. Moreover, CeCas12a is revealed to be more stringent for PAM recognition in vitro and in vivo followed by very low off-target editing rates in cells. Notably, CeCas12a renders less off-target edits located at C-containing PAM at multiple sites compared to LbCas12a and AsCas12a, as assessed by targeted sequencing methods.ConclusionsOur study shows that CeCas12a nuclease is active in human cells and the stringency of PAM recognition could be an important factor shaping off-target editing in gene editing. Thus, CeCas12a provides a promising candidate with distinctive characteristics for research and therapeutic applications.

| S-EPMC7093978 | biostudies-literature

Cas12a variants designed for lower genome-wide off-target effect through stringent PAM recognition

Project description:Cas12a variants designed for lower genome-wide off-target effect through stringent PAM recognition

| PRJNA769264 | ENA

Randomized PAM depletion of phylogenetically-diverse Cas12a nucleases

Project description:Randomized PAM depletion of phylogenetically-diverse Cas12a nucleases

| PRJNA539942 | ENA

High targeted integration frequency in human pluripotent stem cells with the CRISPR-Cas12a Ultra system

Project description:The CRISPR-Cas12a platform has attracted interest in the genome editing community because the prototypic Acidaminococcus Cas12a generates a staggered DNA double-strand break upon binding to an AT-rich protospacer-adjacent motif (PAM, 5'-TTTV). The broad application of the platform in primary human cells was enabled by the development of an engineered version of the natural Cas12a protein, called Cas12a Ultra. In this study, we confirmed that CRISPR-Cas12a Ultra ribonucleoprotein complexes enabled allelic gene disruption frequencies of over 90% at multiple target sites in human T cells, hematopoietic stem and progenitor cells (HSPCs), and induced pluripotent stem cells (iPSCs). In addition, we demonstrated for the first time the efficient knock-in potential of the platform in human iPSCs and achieved targeted integration of a GFP marker gene into the AAVS1 safe harbor site and a CSF2RA super-exon into CSF2RA in up to 90% of alleles without selection. Clonal analysis revealed bi-allelic integration in >50% of the screened iPSC clones without compromising their pluripotency and genomic integrity. Thus, in combination with the adeno-associated virus vector system, CRISPR-Cas12a Ultra provides a highly efficient genome editing platform for performing targeted knock-ins in human iPSCs.

2024-02-09 | GSE249731 | GEO

The compact high-fidelity EbCas12a enables all-in-one AAV delivery system

Project description:we characterized a novel compact Cas12a ortholog, EbCas12a, from the Erysipelotrichia bacterium with activities in mammalian cells. It is with the PAM sequence of 5’-TTTV-3’ (V=A, G, C) and the smallest size of ~3.47kb among reported Cas12a orthologs so far. Moreover, enhanced EbCas12a (enEbCas12a) was also developed to have comparable editing efficiency with higher specificity to AsCas12a and LbCas12a in mammalian cells. With the help of the compact enEbCas12a, all-in-one AAV delivery system with crRNA for Cas12a was developed for both in vitro and in vivo. Altogether, with the help of the novel smallest high fidelity enEbCas12a, this first case of the all-in-one AAV delivery for Cas12a could greatly boost future gene therapy and scientific research.

2023-07-10 | GSE236647 | GEO

Cas12a base editors induce efficient and specific editing with low DNA damage response (RNA sequencing)

Project description:The advent of base editors (BEs) holds a promising potential in correcting pathogenic-related point mutations to treat relevant diseases. Unexpectedly, Cas9 nickase (nCas9) derived BEs lead to DNA double-strand breaks, which can trigger unwanted cellular responses including a p53-mediated DNA damage response (DDR). Here, we showed that catalytically-dead-Cas12a (dCas12a) conjugated BEs induced no DNA break and minimally activated DDR proteins including H2AX, ATM, ATR and p53. We further developed a BEACON (Base Editing induced by human APOBEC3A and Cas12a without DNA break) system that fuses dCas12a to the engineered APOBEC3A with enhanced deamination efficiency and editing specificity. By using BEACON, efficient C-to-T editing was achieved at levels comparable to AncBE4max and only low levels of DDR and RNA off-target (OT) effects were triggered in mammalian cells. BEACON also induced in vivo base editing in mouse embryos and targeted C-to-T conversions were detected in F0 mice.

2020-05-05 | GSE144278 | GEO

Cas12a base editors induce efficient and specific editing with low DNA damage response (DNA targeted sequencing)

2020-05-05 | GSE145550 | GEO

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