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Found: 26 174
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Applying gene editing to tailor precise genetic modifications in plants.
The ability to tailor alterations in genomes, including plant genomes, in a site-specific manner has been greatly advanced through approaches that reduced the complexity and time of genome sequencing along with development of gene editing technologies. These technologies provide a valuable foundation for studies of gene function, metabolic engineering, and trait modification for crop improvement. Development of genome editing methodologies began ∼20 years ago, first with meganucleases and followed by zinc finger nucleases, transcriptional activator-like effector nucleases and, most recently, clustered regulatory interspaced short palindromic repeat (CRISPR)-associated protein (Cas) (CRISPR/Cas), which is by far the most utilized method. The premise of CRISPR/Cas centers on the cleaving of one or both DNA strands by a Cas protein, an endonuclease, followed by mending of the DNA by repair mechanisms inherent in cells. Its user-friendly construct design, greater flexibility in targeting genomic regions, and cost-effective attributes have resulted in it being widely adopted and revolutionizing precise modification of the genomes of many organisms. Indeed, the CRISPR/Cas system has been utilized for gene editing in many plant species, including important food crops, such as maize, wheat, rice, and potatoes. This review summarizes the various approaches, including the most recent designs being used to make modifications from as small as a single-base-pair change to insertion of DNA fragments. On the gene expression level, strategies are presented that make it possible to knock out or modulate through activation and repression. Also discussed are prerequisites necessary for CRISPR/Cas-mediated editing as well as the current challenges.
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Base editing for reprogramming cyanobacterium Synechococcus elongatus.
Cyanobacteria can directly convert carbon dioxide (CO2) at the atmospheric level to biofuels, value-added chemicals and food products, making them ideal candidates to alleviate global climate change. Despite decades-long pioneering successes, the development of genome-editing tools, especially the CRISPR-Cas-based approaches, seems to lag behind other microbial chassis, slowing down the innovations of cyanobacteria. Here, we adapted and tailored base editing for cyanobacteria based on the CRISPR-Cas system and deamination. We achieved precise and efficient genome editing at a single-nucleotide resolution and demonstrated multiplex base editing in the model cyanobacterium Synechococcus elongatus. By using the base-editing tool, we successfully manipulated the glycogen metabolic pathway via the introduction of premature STOP codons in the relevant genes, building engineered strains with elevated potentials to produce chemicals and food from CO2. We present here the first report of base editing in the phylum of cyanobacteria, and a paradigm for applying CRISPR-Cas systems in bacteria. We believe that our work will accelerate the metabolic engineering and synthetic biology of cyanobacteria and drive more innovations to alleviate global climate change.
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Optimizing plant adenine base editor systems by modifying the transgene selection system.
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[Optimization of CRISPR/Cas9-based multiplex base editing in Corynebacterium glutamicum].
As a new CRISPR/Cas-derived genome engineering technology, base editing combines the target specificity of CRISPR/Cas and the catalytic activity of nucleobase deaminase to install point mutations at target loci without generating DSBs, requiring exogenous template, or depending on homologous recombination. Recently, researchers have developed a variety of base editing tools in the important industrial strain Corynebacterium glutamicum, and achieved simultaneous editing of two and three genes. However, the multiplex base editing based on CRISPR/Cas9 is still limited by the complexity of multiple sgRNAs, interference of repeated sequence and difficulty of target loci replacement. In this study, multiplex base editing in C. glutamicum was optimized by the following strategies. Firstly, the multiple sgRNA expression cassettes based on individual promoters/terminators was optimized. The target loci can be introduced and replaced rapidly by using a template plasmid and Golden Gate method, which also avoids the interference of repeated sequence. Although the multiple sgRNAs structure is still complicated, the editing efficiency of this strategy is the highest. Then, the multiple gRNA expression cassettes based on Type Ⅱ CRISPR crRNA arrays and tRNA processing were developed. The two strategies only require one single promoter and terminator, and greatly simplify the structure of the expression cassette. Although the editing efficiency has decreased, both methods are still applicable. Taken together, this study provides a powerful addition to the genome editing toolbox of C. glutamicum and facilitates genetic modification of this strain.
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Highly efficient C-to-T and A-to-G base editing in a Populus hybrid.
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CRISPR Inversion of CTCF Sites Alters Genome Topology and Enhancer/Promoter Function.
CTCF and the associated cohesin complex play a central role in insulator function and higher-order chromatin organization of mammalian genomes. Recent studies identified a correlation between the orientation of CTCF-binding sites (CBSs) and chromatin loops. To test the functional significance of this observation, we combined CRISPR/Cas9-based genomic-DNA-fragment editing with chromosome-conformation-capture experiments to show that the location and relative orientations of CBSs determine the specificity of long-range chromatin looping in mammalian genomes, using protocadherin (Pcdh) and β-globin as model genes. Inversion of CBS elements within the Pcdh enhancer reconfigures the topology of chromatin loops between the distal enhancer and target promoters and alters gene-expression patterns. Thus, although enhancers can function in an orientation-independent manner in reporter assays, in the native chromosome context, the orientation of at least some enhancers carrying CBSs can determine both the architecture of topological chromatin domains and enhancer/promoter specificity. These findings reveal how 3D chromosome architecture can be encoded by linear genome sequences.
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HMGN1 enhances CRISPR-directed dual-function A-to-G and C-to-G base editing.
C-to-G base editors have been successfully constructed recently, but limited work has been done on concurrent C-to-G and A-to-G base editing. In addition, there is also limited data on how chromatin-associated factors affect the base editing. Here, we test a series of chromatin-associated factors, and chromosomal protein HMGN1 was found to enhance the efficiency of both C-to-G and A-to-G base editing. By fusing HMGN1, GBE and ABE to Cas9, we develop a CRISPR-based dual-function A-to-G and C-to-G base editor (GGBE) which is capable of converting simultaneous A and C to G conversion with substantial editing efficiency. Accordingly, the HMGN1 role shown in this work and the resulting GGBE tool further broaden the genome manipulation capacity of CRISPR-directed base editors.
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Prime editing in bacteria with BacPE.
Programmable genome editing technologies have revolutionized the ability of researchers to alter the genomes of microorganisms in a straightforward and efficient manner, significantly advancing the field of microbiology. To date, several CRISPR-Cas-based genome-editing systems have been developed for use in E. coli, including CRISPR/Cas9, base editing, and prime editing technologies. In this chapter, we describe the design and experimental application of BacPE, a variant of prime editing technology optimized for E. coli. BacPE facilitates the introduction of point mutations, insertions, and deletions without the need for double-strand DNA breaks. We demonstrate that BacPE is a powerful tool for genome editing in E. coli and highlight its potential applicability to other bacterial species.
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Advancing Gene Therapy for Phenylketonuria: From Precision Editing to Clinical Translation.
Phenylketonuria (PKU) is an inherited disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene that result in the amino acid phenylalanine (Phe) building up in the blood. Current therapies suggest low-Phe dietary management and (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) therapy, which are limited in efficacy and require lifelong treatment. Recent advances in gene therapy, including gene editing and viral-mediated gene delivery, produce therapeutic effects. Advancements in gene editing technologies, notably adenine base editors (ABEs) and CRISPR-based systems, in conjunction with enhanced delivery methods such as lipid nanoparticles (LNPs) and recombinant viruses, have demonstrated substantial promise in preclinical studies. This review details the pathophysiology of PKU treatment, and progress in preclinical and clinical gene therapy strategies. Emphasis is on adenine base editing using LNPs, recombinant adeno-associated virus (rAAV)-mediated gene transfer, and the translational challenges associated with these technologies. We also discuss future directions for therapeutic reach and ensuring long-term safety and efficacy.
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Efficient A·T-to-C·G Base Editing via Adenine Transversion Editors.
Generating A-to-C transversions to correct defective alleles or introduce novel alleles has posed significant challenges. However, two recent studies focusing on adenine transversions have achieved successful A-to-C transversions in mouse embryos and plant cell. These remarkable accomplishments notably broaden the range of base editing and their applications both in fundamental research and in therapeutics.
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