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Advances in precise regulation of CRISPR/Cas9 gene editing technology.
Gene editing is a genetic engineering technology that can modify, delete, or insert a small piece of DNA at a specific point in the genome of cells and organisms. Gene editing technology holds great promises in the fields of disease treatment, gene function regulation, gene detection, drug research and development, and crop breeding. However, side effects, such as off-target editing, genotoxicity and other issues, have gradually emerged in the application. In the CRISPR (clustered regularly interspaced short palindromic repeats) system, the Cas9 nuclease can specifically recognize the target DNA by the base pairing of a guide RNA (gRNA) with the target DNA. Upon target recognition, the two DNA strands are cleaved by distinct domains of the Cas9 nuclease. Since both Cas9 nuclease and gRNA possess different characteristics in their own activities, recognition sites and binding ability to specific target, it is essential to precisely regulate the activity of Cas9 nuclease and gRNA in both time and space manners, thus preventing the risk of side effects and enhancing the precise regulation of the CRISPR/Cas9 gene editing technology. In this review, we summarize the advances in the precise control of gene editing, especially CRISPR/cas9 over several dimensions using fusion Cas9 proteins regulated by light, temperature and drugs, exploiting and screening anti-CRISPRs proteins, synthesizing and identifying small molecules- inhibitors, and developing other therapeutic agents, thereby providing a reference and research ideas for human disease treatment, crop and livestock improvement and prevention of biotechnology misuse.
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CRISPR Detection From Short Reads Using Partial Overlap Graphs.
Clustered regularly interspaced short palindromic repeats (CRISPR) are structured regions in bacterial and archaeal genomes, which are part of an adaptive immune system against phages. CRISPRs are important for many microbial studies and are playing an essential role in current gene editing techniques. As such, they attract substantial research interest. The exponential growth in the amount of bacterial sequence data in recent years enables the exploration of CRISPR loci in more and more species. Most of the automated tools that detect CRISPR loci rely on fully assembled genomes. However, many assemblers do not handle repetitive regions successfully. The first tool to work directly on raw sequence data is Crass, which requires reads that are long enough to contain two copies of the same repeat. We present a method to identify CRISPR repeats from raw sequence data of short reads. The algorithm is based on an observation differentiating CRISPR repeats from other types of repeats, and it involves a series of partial constructions of the overlap graph. This enables us to avoid many of the difficulties that assemblers face, as we merely aim to identify the repeats that belong to CRISPR loci. A preliminary implementation of the algorithm shows good results and detects CRISPR repeats in cases where other existing tools fail to do so.
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Targeted Nucleotide Editing Technologies for Microbial Metabolic Engineering.
Since the emergence of programmable RNA-guided nucleases based on clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) systems, genome editing technologies have become a simplified and versatile tool for genome editing in various organisms and cell types. Although genome editing enables efficient genome manipulations, such as gene disruptions, gene knockins, and chromosomal translocations via DNA double-strand break (DSB) repair in eukaryotes, DSBs induced by the CRISPR/Cas system are lethal or severely toxic to many microorganisms. Therefore, in many prokaryotes, including industrially useful microbes, the CRISPR/Cas system is often used as a negative selection component in combination with recombineering or other related strategies. Novel and revolutionary technologies have been recently developed to re-write targeted nucleotides (C:G to T:A and A:T to G:C) without DSBs and donor DNA templates. These technologies rely on the recruitment of deaminases at specific target loci using the nuclease-deficient CRISPR/Cas system. Here, the authors review and compare CRISPR-based genome editing, current base editing platforms and their spectra. The authors discuss how these technologies can be applied in various aspects of microbial metabolic engineering to overcome barriers to cellular regulation in prokaryotes.
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Progress and Perspective of CRISPR-Cas9 Technology in Translational Medicine.
Translational medicine aims to improve human health by exploring potential treatment methods developed during basic scientific research and applying them to the treatment of patients in clinical settings. The advanced perceptions of gene functions have remarkably revolutionized clinical treatment strategies for target agents. However, the progress in gene editing therapy has been hindered due to the severe off-target effects and limited editing sites. Fortunately, the development in the clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR-Cas9) system has renewed hope for gene therapy field. The CRISPR-Cas9 system can fulfill various simple or complex purposes, including gene knockout, knock-in, activation, interference, base editing, and sequence detection. Accordingly, the CRISPR-Cas9 system is adaptable to translational medicine, which calls for the alteration of genomic sequences. This review aims to present the latest CRISPR-Cas9 technology achievements and prospect to translational medicine advances. The principle and characterization of the CRISPR-Cas9 system are firstly introduced. The authors then focus on recent pre-clinical and clinical research directions, including the construction of disease models, disease-related gene screening and regulation, and disease treatment and diagnosis for multiple refractory diseases. Finally, some clinical challenges including off-target effects, in vivo vectors, and ethical problems, and future perspective are also discussed.
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Targeted Mutagenesis in Mice Using a Base Editor.
Base editors, such as cytosine and adenine base editors, are composed of nickase Cas9 (nCas9) and deaminase and serve as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based enzymatic tools for specific nucleotide substitutions. They are mainly the most effective genome editing tools for introducing point mutations, such as C-to-T and A-to-G conversions. The enhanced base editor, a C-to-G base editor (CGBE), can perform other nucleotide substitutions, such as C-to-G conversions. Here, we introduce a method for generating mouse models with point mutations using a base editing system.
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CRISPR-Cas9 DNA Base-Editing and Prime-Editing.
Many genetic diseases and undesirable traits are due to base-pair alterations in genomic DNA. Base-editing, the newest evolution of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas-based technologies, can directly install point-mutations in cellular DNA without inducing a double-strand DNA break (DSB). Two classes of DNA base-editors have been described thus far, cytosine base-editors (CBEs) and adenine base-editors (ABEs). Recently, prime-editing (PE) has further expanded the CRISPR-base-edit toolkit to all twelve possible transition and transversion mutations, as well as small insertion or deletion mutations. Safe and efficient delivery of editing systems to target cells is one of the most paramount and challenging components for the therapeutic success of BEs. Due to its broad tropism, well-studied serotypes, and reduced immunogenicity, adeno-associated vector (AAV) has emerged as the leading platform for viral delivery of genome editing agents, including DNA-base-editors. In this review, we describe the development of various base-editors, assess their technical advantages and limitations, and discuss their therapeutic potential to treat debilitating human diseases.
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Characterization and engineering of highly efficient Cas12j genome editors.
The large size of widely used CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) enzymes limits their delivery for therapeutic applications. Cas12j nucleases offer a hypercompact alternative but show modest editing efficiency. To overcome this limitation, we identified eight novel Cas12j orthologs from viral metagenomes, which in their native form exhibit low editing activity in mammalian cells. We therefore engineered T5 exonuclease-Cas12j fusions, resulting in substantially enhanced genome-editing activity across multiple mammalian cell types, reaching levels comparable to established compact CRISPR-Cas editors. Intriguingly, robust cellular editing occurred in the presence of a previously unrecognized trinucleotide sequence context within the target DNA. Furthermore, we developed Cas12j-based adenine base editors by coupling catalytically inactive Cas12j orthologs with adenine deaminase, enabling efficient A-to-G base conversion in mammalian cells. This study expands the CRISPR toolbox by establishing engineering principles that convert compact Cas12j nucleases into efficient and modular genome-editing platforms well suited for delivery-constrained therapeutic applications.
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CRISPR/Cas system-mediated base editing in crops: recent developments and future prospects.
Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (CRISPR/Cas9) genome-editing system has altered plant research by allowing for targeted genome alteration, and they are emerging as powerful tools for evaluating plant gene function and improving crop yield. Even though CRISPR/Cas9 cleavage and subsequent repair are effective ways to precisely replace genes and change base pairs in plants, the dominance of the non-homologous end-joining pathway (NHEJ) and homology-directed repair's (HDR) poor effectiveness in plant cells have restricted their use. Base editing is gaining popularity as a potential alternative to HDR or NHEJ-mediated replacement, allowing for precise changes in the plant genome via programmed conversion of a single base to another without the need for a donor repair template or double-stranded breaks. In this review, we primarily present the mechanisms of base-editing system, including their distinct types such as DNA base editors (cytidine base editor and adenine base editor) and RNA base editors discovered so far. Next, we outline the current potential applications of the base-editing system for crop improvements. Finally, we discuss the limitations and potential future directions of the base-editing system in terms of improving crop quality. We hope that this review will enable the researcher to gain knowledge about base-editing tools and their potential applications in crop improvement.
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Recent advances in CRISPR-based genome editing technology and its applications in cardiovascular research.
The rapid development of genome editing technology has brought major breakthroughs in the fields of life science and medicine. In recent years, the clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing toolbox has been greatly expanded, not only with emerging CRISPR-associated protein (Cas) nucleases, but also novel applications through combination with diverse effectors. Recently, transposon-associated programmable RNA-guided genome editing systems have been uncovered, adding myriads of potential new tools to the genome editing toolbox. CRISPR-based genome editing technology has also revolutionized cardiovascular research. Here we first summarize the advances involving newly identified Cas orthologs, engineered variants and novel genome editing systems, and then discuss the applications of the CRISPR-Cas systems in precise genome editing, such as base editing and prime editing. We also highlight recent progress in cardiovascular research using CRISPR-based genome editing technologies, including the generation of genetically modified in vitro and animal models of cardiovascular diseases (CVD) as well as the applications in treating different types of CVD. Finally, the current limitations and future prospects of genome editing technologies are discussed.
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Improvements in health-related quality of life in patients with severe sickle cell disease after exagamglogene autotemcel.
Severe sickle cell disease (SCD), an inherited blood disorder characterized by recurrent vaso-occlusive crises (VOCs), significantly impairs health-related quality of life (HRQoL). Exagamglogene autotemcel (exa-cel), a one-time, ex vivo CRISPR/Cas9 gene-edited cell therapy, eliminated VOCs in 97% of participants with severe SCD in the phase 3 CLIMB SCD-121 trial. Here, we describe changes in patient-reported outcomes (PROs) in 30 adults and 12 adolescents with ≥16 months follow-up. Adult PROs include EuroQol Quality of Life Scale-5 dimensions-5 levels of severity (EQ-5D-5L), Functional Assessment of Cancer Therapy Bone Marrow Transplant (FACT-BMT), Adult Sickle Cell Quality of Life Measurement Information System (ASCQ-Me), and 11-point pain Numerical Rating Scale (NRS). In adolescents, EuroQol Quality of Life Scale-5 dimensions-youth (EQ-5D-Y), Pediatric Quality of Life Inventory (PedsQL), and pain NRS were used. Adult EQ-5D-5L US and UK healthy utility index and EQ visual analog scale (VAS) scores, which were lower than general population norm at baseline, substantially improved by month 6 after exa-cel infusion and were sustained through month 36, with similar improvements in FACT-General (FACT-G) total and bone marrow transplant subscale. All FACT-G (physical, social/family, emotional, functional well-being) and ASCQ-Me (emotional, social functioning, stiffness, sleep impact) subscales showed clinically meaningful improvement, including ASCQ-Me pain subscales (impact, episode frequency, severity), with substantial decreases in pain episode frequency by month 6. Mean pain NRS score decreased by month 6 and was sustained. Consistent with adults, adolescents had improvements in mean EQ-5D-Y VAS score, PedsQL score, and pain NRS. Exa-cel led to broad and clinically meaningful HRQoL benefits in adults and adolescents with SCD. The CLIMB SCD-121 and CLIMB-131 trials were registered at www.clinicaltrials.gov as #NCT03745287 and #NCT04208529, respectively.
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