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Efficient CRISPR-Cas9 based cytosine base editors for phytopathogenic bacteria.
Phytopathogenic bacteria play important roles in plant productivity, and developments in gene editing have potential for enhancing the genetic tools for the identification of critical genes in the pathogenesis process. CRISPR-based genome editing variants have been developed for a wide range of applications in eukaryotes and prokaryotes. However, the unique mechanisms of different hosts restrict the wide adaptation for specific applications. Here, CRISPR-dCas9 (dead Cas9) and nCas9 (Cas9 nickase) deaminase vectors were developed for a broad range of phytopathogenic bacteria. A gene for a dCas9 or nCas9, cytosine deaminase CDA1, and glycosylase inhibitor fusion protein (cytosine base editor, or CBE) was applied to base editing under the control of different promoters. Results showed that the RecA promoter led to nearly 100% modification of the target region. When residing on the broad host range plasmid pHM1, CBERecAp is efficient in creating base edits in strains of Xanthomonas, Pseudomonas, Erwinia and Agrobacterium. CBE based on nCas9 extended the editing window and produced a significantly higher editing rate in Pseudomonas. Strains with nonsynonymous mutations in test genes displayed expected phenotypes. By multiplexing guide RNA genes, the vectors can modify up to four genes in a single round of editing. Whole-genome sequencing of base-edited isolates of Xanthomonas oryzae pv. oryzae revealed guide RNA-independent off-target mutations. Further modifications of the CBE, using a CDA1 variant (CBERecAp-A) reduced off-target effects, providing an improved editing tool for a broad group of phytopathogenic bacteria.
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Effective therapies for sickle cell disease: are we there yet?
Sickle cell disease (SCD) is a common genetic blood disorder associated with acute and chronic pain, progressive multiorgan damage, and early mortality. Recent advances in technologies to manipulate the human genome, a century of research and the development of techniques enabling the isolation, efficient genetic modification, and reimplantation of autologous patient hematopoietic stem cells (HSCs), mean that curing most patients with SCD could soon be a reality in wealthy countries. In parallel, ongoing research is pursuing more facile treatments, such as in-vivo-delivered genetic therapies and new drugs that can eventually be administered in low- and middle-income countries where most SCD patients reside.
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Design of highly functional genome editors by modelling CRISPR-Cas sequences.
Gene editing has the potential to solve fundamental challenges in agriculture, biotechnology and human health. CRISPR-based gene editors derived from microorganisms, although powerful, often show notable functional tradeoffs when ported into non-native environments, such as human cells1. Artificial-intelligence-enabled design provides a powerful alternative with the potential to bypass evolutionary constraints and generate editors with optimal properties. Here, using large language models2 trained on biological diversity at scale, we demonstrate successful precision editing of the human genome with a programmable gene editor designed with artificial intelligence. To achieve this goal, we curated a dataset of more than 1 million CRISPR operons through systematic mining of 26 terabases of assembled genomes and metagenomes. We demonstrate the capacity of our models by generating 4.8× the number of protein clusters across CRISPR-Cas families found in nature and tailoring single-guide RNA sequences for Cas9-like effector proteins. Several of the generated gene editors show comparable or improved activity and specificity relative to SpCas9, the prototypical gene editing effector, while being 400 mutations away in sequence. Finally, we demonstrate that an artificial-intelligence-generated gene editor, denoted as OpenCRISPR-1, exhibits compatibility with base editing. We release OpenCRISPR-1 to facilitate broad, ethical use across research and commercial applications.
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Using Gene Editing Approaches to Fine-Tune the Immune System.
Genome editing technologies not only provide unprecedented opportunities to study basic cellular system functionality but also improve the outcomes of several clinical applications. In this review, we analyze various gene editing techniques used to fine-tune immune systems from a basic research and clinical perspective. We discuss recent advances in the development of programmable nucleases, such as zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeat (CRISPR)-Cas-associated nucleases. We also discuss the use of programmable nucleases and their derivative reagents such as base editing tools to engineer immune cells via gene disruption, insertion, and rewriting of T cells and other immune components, such natural killers (NKs) and hematopoietic stem and progenitor cells (HSPCs). In addition, with regard to chimeric antigen receptors (CARs), we describe how different gene editing tools enable healthy donor cells to be used in CAR T therapy instead of autologous cells without risking graft-versus-host disease or rejection, leading to reduced adoptive cell therapy costs and instant treatment availability for patients. We pay particular attention to the delivery of therapeutic transgenes, such as CARs, to endogenous loci which prevents collateral damage and increases therapeutic effectiveness. Finally, we review creative innovations, including immune system repurposing, that facilitate safe and efficient genome surgery within the framework of clinical cancer immunotherapies.
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A Multiplexed Cas13-Based Assay with Point-of-Care Attributes for Simultaneous COVID-19 Diagnosis and Variant Surveillance.
Point-of-care (POC) nucleic acid detection technologies are poised to aid gold-standard technologies in controlling the COVID-19 pandemic, yet shortcomings in the capability to perform critically needed complex detection-such as multiplexed detection for viral variant surveillance-may limit their widespread adoption. Herein, we developed a robust multiplexed clustered regularly interspaced short palindromic repeats (CRISPR)-based detection using LwaCas13a and PsmCas13b to simultaneously diagnose severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and pinpoint the causative SARS-CoV-2 variant of concern (VOC)-including globally dominant VOCs Delta (B.1.617.2) and Omicron (B.1.1.529)-all the while maintaining high levels of accuracy upon the detection of multiple SARS-CoV-2 gene targets. The platform has several attributes suitable for POC use: premixed, freeze-dried reagents for easy use and storage; convenient direct-to-eye or smartphone-based readouts; and a one-pot variant of the multiplexed detection. To reduce reliance on proprietary reagents and enable sustainable use of such a technology in low- and middle-income countries, we locally produced and formulated our own recombinase polymerase amplification reaction and demonstrated its equivalent efficiency to commercial counterparts. Our tool-CRISPR-based detection for simultaneous COVID-19 diagnosis and variant surveillance that can be locally manufactured-may enable sustainable use of CRISPR diagnostics technologies for COVID-19 and other diseases in POC settings.
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CRISPR/Cas9 gene editing for genodermatoses: progress and perspectives.
Genodermatoses constitute a clinically heterogeneous group of devastating genetic skin disorders. Currently, therapy options are largely limited to symptomatic treatments and although significant advances have been made in ex vivo gene therapy strategies, various limitations remain. However, the recent technical transformation of the genome editing field promises to overcome the hurdles associated with conventional gene addition approaches. In this review, we discuss the need for developing novel treatments and describe the current status of gene editing for genodermatoses, focusing on a severe blistering disease called epidermolysis bullosa (EB), for which significant progress has been made. Initial research utilized engineered nucleases such as transcription activator-like effector nucleases and meganucleases. However, over the last few years, clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) have upstaged older generation gene editing tools. We examine different strategies for CRISPR/Cas9 application that can be employed depending on the type and position of the mutation as well as the mode of its inheritance. Promising developments in the field of base editing opens new avenues for precise correction of single base substitutions, common in EB and other genodermatoses. We also address the potential limitations and challenges such as safety concerns and delivery efficiency. This review gives an insight into the future of gene editing technologies for genodermatoses.
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Highly efficient base editing with expanded targeting scope using SpCas9-NG in rabbits.
Base editors, composed of a cytidine deaminase or an evolved adenine deaminase fused to Cas9 nickase, enable efficient C-to-T or A-to-G conversion in various organisms. However, the NGG protospacer adjacent motif (PAM) requirement of Streptococcus pyogenes Cas9 (SpCas9) substantially limits the target sites suitable for base editing. Quite recently, a new engineered SpCas9-NG variant, which can recognize minimal NG PAMs more efficiently than the present xCas9 variant. Here, we investigated the efficiency and PAM compatibility of SpCas9-NG-assisted cytidine base editors (CBEs) and adenine base editors (ABEs) in rabbits. In this study, we showed that NG-BE4max and NG-ABEmax systems can achieve a targeted mutation efficiency of 75%-100% and 80%-100% with excellent PAM compatibility of NGN PAMs in rabbit embryos, respectively. In addition, both base editors were successfully applied to create new rabbit models with precise point mutations, demonstrating their high efficiency and expanded genome-targeting scope in rabbits. Meanwhile, NG-ABEmax can be used to precisely mimic human Hoxc13 p.Q271R missense mutation in Founder (F0) rabbits, which is arduous for conventional ABEs to achieve due to a NGA PAM requirement. Collectively, NG-BE4max and NG-ABEmax systems provide promising tools to perform efficient base editing with expanded targeting scope in rabbits and enhances its capacity to model human diseases.
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A side-by-side comparison of variant function measurements using deep mutational scanning and base editing.
Variant annotation is a crucial objective in mammalian functional genomics. Deep mutational scanning (DMS) using saturation libraries of complementary DNAs (cDNAs) is a well-established method for annotating human gene variants, but CRISPR base editing (BE) is emerging as an alternative. However, questions remain about how well high-throughput BE measurements can annotate variant function and the extent of downstream experimental validation required. This study is the first direct comparison of cDNA DMS and BE in the same lab and cell line. We focus on how well short guide RNA (sgRNA) depletion or enrichment is explained by the predicted edits within the editing "window" defined by the sgRNA. The most likely predicted edits enhance the agreement between a "gold standard" DMS dataset and a BE screen. A simple filter for sgRNAs making single edits in their window could sufficiently annotate a large proportion of variants directly from sgRNA sequencing of large pools. When multi-edit guides are unavoidable, directly measuring edits in medium-sized validation pools can recover high-quality variant annotation data. Our data show a surprisingly high degree of correlation between base editor data and gold standard DMS. We suggest that the main variable measured in base editor screens is the desired base edits.
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Reporter-based screening identifies small-molecule CBL0137 as an enhancer of CRISPR cytosine base editor and prime editor via p53 activation and NF-κB inhibition.
Recently developed CRISPR base editors (BEs) and prime editors (PEs) enable precise genome editing without inducing double-strand breaks, making them highly promising tools for therapeutic applications. However, their efficiency remains a major barrier to clinical translation, particularly at difficult-to-target sites. To address this limitation, we used a high-throughput GFP reporter system responsive to cytosine base editor (CBE) activity to screen small molecules involved in DNA damage response, cell cycle, and apoptosis pathways. This screen identified CBL0137 as a candidate that significantly enhanced editing efficiency at both the reporter and endogenous target sites, with up to an 80 % improvement. Mechanistic studies revealed that CBL0137 acts through activation of the p53 pathway and inhibition of NF-κB. Interestingly, the enhancement was largely specific to CBEs, while in PEs, CBL0137 selectively improved multi-site mutations and fragment insertions without affecting single-point edits or deletions. Collectively, these results identify CBL0137 as a selective enhancer of specific genome editing activities, providing a strategy to increase editing efficiency and advancing the translational potential of next-generation genome editing tools for therapeutic applications.
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Identification of optimal adenine and cytosine base editors for genome editing in Arabidopsis and soybean.
Base editors, including adenine base editors (ABEs) and cytosine base editors (CBEs), are widely used in numerous organisms to introduce site-specific sequence modifications in genomic DNA without causing double-strand breaks (DSBs). However, these editors exhibit low editing efficiencies, particularly in dicot plants, thereby limiting their application in dicot plant genome engineering. In this study, we assessed the editing efficiencies of various base editors to identify those optimal for base editing in dicot plants. We discovered that ABE8e, an ABE variant, demonstrated superior A-to-G base editing efficiency within A5-A8 windows, and A3A/Y130F-V04, a CBE variant, exhibited the highest C-to-T base editing efficiency within C4-C15 windows in both Arabidopsis and soybean protoplasts. Overall, we recommend these two base editors as prime choices for efficient genome engineering in a range of crop plants. [BMB Reports 2025; 58(7): 288-292].
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