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Comprehensive evaluation and prediction of editing outcomes for near-PAMless adenine and cytosine base editors.
Base editors enable the direct conversion of target bases without inducing double-strand breaks, showing great potential for disease modeling and gene therapy. Yet, their applicability has been constrained by the necessity for specific protospacer adjacent motif (PAM). We generate four versions of near-PAMless base editors and systematically evaluate their editing patterns and efficiencies using an sgRNA-target library of 45,747 sequences. Near-PAMless base editors significantly expanded the targeting scope, with both PAM and target flanking sequences as determinants for editing outcomes. We develop BEguider, a deep learning model, to accurately predict editing results for near-PAMless base editors. We also provide experimentally measured editing outcomes of 20,541 ClinVar sites, demonstrating that variants previously inaccessible by NGG PAM base editors can now be precisely generated or corrected. We make our predictive tool and data available online to facilitate development and application of near-PAMless base editors in both research and clinical settings.
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Mitochondrial genome editing tools: prospects in animal breeding.
Mitochondria are vital organelles responsible for driving cellular energy metabolism and regulating key biological processes. Their circular mitochondrial DNA (mtDNA) encodes 13 subunits of the respiratory chain proteins but is susceptible to mutations due to high levels of reactive oxygen species and limited repair mechanisms. Mutant phenotypes manifest only when heteroplasmy surpasses a critical threshold. Understanding the consequences of mtDNA mutations has long been hampered by the lack of precise editing tools. Recently, CRISPR-free, protein-only mitochondrial base editors have enabled C·G-to-T·A and A·T-to-G·C transitions. These breakthroughs facilitate the creation of relevant disease models and offer unique opportunities for animal breeding, as specific mtDNA variants are known to influence economically important traits in livestock, including production, reproduction, and stress tolerance. This review summarizes recent advances in mitochondrial genome editing technologies, including CRISPR/Cas-based systems, restriction endonucleases, double-stranded DNA deaminase toxin A (DddA)-based cytosine and adenine base editors, and DddA-free base editors, along with their delivery strategies and optimization avenues. Furthermore, we outline the associations between mtDNA polymorphisms, copy number variation, and economic traits in livestock and poultry. Finally, we discuss the potential applications of mitochondrial genome editing in animal breeding and highlight the critical safety and ethical considerations that require careful attention.
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Diverse Class 2 CRISPR Effectors as Active Nucleases with Expanded Targeting Capabilities.
CRISPR-Cas systems have proven effective in a variety of applications due to their ease of use and relatively high editing efficiency. Yet, any individual CRISPR-Cas system has inherent limitations, necessitating a diversity of RNA-guided nucleases to suit applications with distinct needs. We searched through metagenomic sequences to identify RNA-guided nucleases and found enzymes from diverse CRISPR-Cas types and subtypes, the most promising of which we developed into gene-editing platforms. Based on prior annotations of the metagenomic sequences, we establish the likely taxa and sampling locations where Class 2 CRISPR-Cas systems active in eukaryotes may be found. The newly discovered systems show robust capabilities as gene editors and base editors.
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Efficient genome editing in the olive fruit fly, Bactrocera oleae.
The olive fruit fly, Bactrocera oleae, causes great damage to the quality and quantity of olive production worldwide. Pest management approaches have proved difficult for a variety of reasons, a fact that has brought about a need for alternative tools and approaches. Here we report for the first time in B. oleae the development of the clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) gene editing tool, using the well-known eye colour marker gene scarlet. Two synthetic guide RNAs targeting the coding region of the scarlet gene were synthesized and shown to work efficiently in vitro. These reagents were then microinjected along with purified Cas9 protein into early-stage embryos. Successful CRISPR-induced mutations of both copies of the scarlet gene showed a striking yellow eye phenotype, indicative of gene disruption. Multiple successful CRISPR events were confirmed by PCR and sequencing. The establishment of an efficient CRISPR-based gene editing tool in B. oleae will enable the study of critical molecular mechanisms in olive fruit fly biology and physiology, including the analysis of insecticide resistance mechanisms and the discovery of novel insecticide targets, as well as facilitate the development of novel biotechnology-based pest control strategies.
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Fast and Quantitative Identification of Ex Vivo Precise Genome Targeting-Induced Indel Events by IDAA.
Recent developments in gene targeting methodologies such as ZFNs, TALENs, and CRISPR/Cas9 have revolutionized approaches for gene modifications in cells, tissues, and whole animals showing great promise for translational applications. With regard to CRISPR/Cas9, a variety of repurposed systems have been developed to achieve gene knock-out, base editing, targeted knock-in, gene activation/repression, epigenetic modulation, and locus-specific labeling. A functional communality of all CRISPR/Cas9 applications is the gRNA-dependent targeting specificity of the Cas9/gRNA complex that, for gene knock-out (KO) purposes, has been shown to dictate the indel formation potential. Therefore, the objective of a CRISPR/Cas9 KO set up is to identify gRNA designs that enable maximum out-of-frame insertion and/or deletion (indel) formation and thus, gRNA design becomes a proxy for optimal functionality of CRISPR/Cas9 KO and repurposed systems. To this end, validation of gRNA functionality depends on efficient, accurate, and sensitive identification of indels induced by a given gRNA design. For in vitro indel profiling the most commonly used methods are based on amplicon size discrimination or sequencing. Indel detection by amplicon analysis (IDAA™) is an alternative sensitive, fast, and cost-efficient approach ideally suited for profiling of indels induced by Cas9/gRNA with similar sensitivity, specificity, and resolution, down to single base discrimination, as the preferred next-generation sequencing-based indel profiling methodologies. Here we provide a protocol that is based on complexed Cas9/gRNA RNPs delivered to primary peripheral blood mononuclear cells (PBMCs) isolated from healthy individuals followed by quantitative IDAA indel profiling. Importantly, the protocol described benefits from a short "sample-to-data" turnaround time of less than 5 h. Thus, this protocol describes a methodology that provides a suitable and effective solution to validate and quantify the extent of ex vivo CRISPR/Cas9 targeting in primary cells.
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Multiplex CRISPR-Cas Genome Editing: Next-Generation Microbial Strain Engineering.
Genome editing is a crucial technology for obtaining desired phenotypes in a variety of species, ranging from microbes to plants, animals, and humans. With the advent of CRISPR-Cas technology, it has become possible to edit the intended sequence by modifying the target recognition sequence in guide RNA (gRNA). By expressing multiple gRNAs simultaneously, it is possible to edit multiple targets at the same time, allowing for the simultaneous introduction of various functions into the cell. This can significantly reduce the time and cost of obtaining engineered microbial strains for specific traits. In this review, we investigate the resolution of multiplex genome editing and its application in engineering microorganisms, including bacteria and yeast. Furthermore, we examine how recent advancements in artificial intelligence technology could assist in microbial genome editing and engineering. Based on these insights, we present our perspectives on the future evolution and potential impact of multiplex genome editing technologies in the agriculture and food industry.
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Enhanced Bombyx genome editing via Cas9 ribonucleoprotein injection.
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Establishment of an efficient Agrobacterium-mediated transformation system and CRISPR/Cas9-mediated genome editing of the OvPDS1 gene in Oxalis vulcanicola 'Sunset Velvet'.
This study overcomes a key technical barrier by establishing transformation and enabling first CRISPR/Cas9 editing in Oxalis, providing a platform for functional genomics and breeding. The lack of an efficient genetic transformation system has considerably hindered functional genomics studies in Oxalis vulcanicola 'Sunset Velvet'. Here, we established a stable and efficient Agrobacterium-mediated transformation system using stem segments as explants. Key parameters, including pre-culture duration, infection time, Agrobacterium cell density, acetosyringone (AS) concentration, and co-cultivation period, were systematically optimized. Under optimal conditions, the highest transient β-glucuronidase (GUS) expression rate reached approximately 9.0%, and eight stable transgenic lines were successfully obtained. CRISPR/Cas9-mediated genome editing was achieved in Oxalis for the first time. Targeted mutagenesis of OvPDS1, a gene involved in carotenoid biosynthesis, resulted in an albino phenotype, and Sanger sequencing confirmed a base substitution at the target site. Although the editing efficiency was relatively low (0.5%), this result demonstrates the feasibility of genome editing in Oxalis. This study overcomes a major technical bottleneck and provides a robust platform for functional gene analysis, trait improvement, and molecular breeding in O. vulcanicola 'Sunset Velvet' and other non-model ornamental plants.
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Single-Nucleotide Microbial Genome Editing Using CRISPR-Cas12a.
Microbial genome editing can be achieved by donor DNA-directed mutagenesis and CRISPR-Cas12a-mediated negative selection. Single-nucleotide-level genome editing enables the manipulation of microbial cells exactly as designed. Here, we describe single-nucleotide substitutions/indels in the target DNA of E. coli genome using a mutagenic DNA oligonucleotide donor and truncated crRNA/Cas12a system. The maximal truncation of nucleotides at the 3'-end of the crRNA enables Cas12a-mediated single-nucleotide-level precise editing at galK targets in the genome of E. coli.
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Genome editing in rice using CRISPR/Cas12i3.
The CRISPR/Cas type V-I is a family of programmable nuclease systems that prefers a T-rich protospacer adjacent motif (PAM) and is guided by a short crRNA. In this study, the genome-editing application of Cas12i3, a type V-I family endonuclease, was characterized in rice. We developed a CRIPSR/Cas12i3-based Multiplex direct repeats (DR)-spacer Array Genome Editing (iMAGE) system that was efficient in editing various genes in rice. Interestingly, iMAGE produced chromosomal structural variations with a higher frequency than CRISPR/Cas9. In addition, we developed base editors using deactivated Cas12i3 and generated herbicide-resistant rice plants using the base editors. These CRIPSR/Cas12i3-based genome editing systems will facilitate precision molecular breeding in plants.
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