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Transforming plant biology and breeding with CRISPR/Cas9, Cas12 and Cas13.
Currently, biology is revolutionized by ever growing applications of the CRISPR/Cas system. As discussed in this Review, new avenues have opened up for plant research and breeding by the use of the sequence-specific DNases Cas9 and Cas12 (formerly named Cpf1) and, more recently, the RNase Cas13 (formerly named C2c2). Although double strand break-induced gene editing based on error-prone nonhomologous end joining has been applied to obtain new traits, such as powdery mildew resistance in wheat or improved pathogen resistance and increased yield in tomato, improved technologies based on CRISPR/Cas for programmed change in plant genomes via homologous recombination have recently been developed. Cas9- and Cas12- mediated DNA binding is used to develop tools for many useful applications, such as transcriptional regulation or fluorescence-based imaging of specific chromosomal loci in plant genomes. Cas13 has recently been applied to degrade mRNAs and combat viral RNA replication. By the possibility to address multiple sequences with different guide RNAs and by the simultaneous use of different Cas proteins in a single cell, we should soon be able to achieve complex changes of plant metabolism in a controlled way.
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The Synergy between CRISPR and Chemical Engineering.
Gene therapy and transgenic research have advanced quickly in recent years due to the development of CRISPR technology. The rapid development of CRISPR technology has been largely benefited by chemical engineering. Firstly, chemical or synthetic substance enables spatiotemporal and conditional control of Cas9 or dCas9 activities. It prevents the leaky expression of CRISPR components, as well as minimizes toxicity and off-target effects. Multi-input logic operations and complex genetic circuits can also be implemented via multiplexed and orthogonal regulation of target genes. Secondly, rational chemical modifications to the sgRNA enhance gene editing efficiency and specificity by improving sgRNA stability and binding affinity to on-target genomic loci, and hence reducing off-target mismatches and systemic immunogenicity. Chemically-modified Cas9 mRNA is also more active and less immunogenic than the native mRNA. Thirdly, nonviral vehicles can circumvent the challenges associated with viral packaging and production through the delivery of Cas9-sgRNA ribonucleoprotein complex or large Cas9 expression plasmids. Multi-functional nanovectors enhance genome editing in vivo by overcoming multiple physiological barriers, enabling ligand-targeted cellular uptake, and blood-brain barrier crossing. Chemical engineering can also facilitate viral-based delivery by improving vector internalization, allowing tissue-specific transgene expression, and preventing inactivation of the viral vectors in vivo. This review aims to discuss how chemical engineering has helped improve existing CRISPR applications and enable new technologies for biomedical research. The usefulness, advantages, and molecular action for each chemical engineering approach are also highlighted.
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Simple, fast and efficient iTOP-mediated delivery of CRISPR/Cas9 RNP in difficult-to-transduce human cells including primary T cells.
The advent of the CRISPR/Cas9 system has transformed the field of human genome engineering and has created new perspectives in the development of innovative cell therapies. However, the absence of a simple, fast and efficient delivery method of CRISPR/Cas9 into primary human cells has been limiting the progress of CRISPR/Cas9-based therapies. Here, we describe an optimized protocol for iTOP-mediated delivery of CRISPR/Cas9 in various human cells, including primary T cells, induced pluripotent stem cells (hiPSCs), Jurkat, ARPE-19 and HEK293 cells. We compare iTOP to other CRISPR/Cas9 delivery methods, such as electroporation and lipofection, and evaluate the corresponding gene-editing efficiencies and post-treatment cell viabilities. We demonstrate that the gene editing achieved by iTOP-mediated delivery of CRISPR/Cas9 is 40-95 % depending on the cell type, while post-iTOP cell viability remains high in the range of 70-95 %. Collectively, we present an optimized workflow for a simple, high-throughput and effective iTOP-mediated delivery of CRISPR/Cas9 to engineer difficult-to-transduce human cells. We believe that the iTOP technology® could contribute to the development of novel CRISPR/Cas9-based cell therapies.
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The Bibliometric Landscape of Gene Editing Innovation and Regulation in the Worldwide.
Gene editing (GE) has become one of the mainstream bioengineering technologies over the past two decades, mainly fueled by the rapid development of the CRISPR/Cas system since 2012. To date, plenty of articles related to the progress and applications of GE have been published globally, but the objective, quantitative and comprehensive investigations of them are relatively few. Here, 13,980 research articles and reviews published since 1999 were collected by using GE-related queries in the Web of Science. We used bibliometric analysis to investigate the competitiveness and cooperation of leading countries, influential affiliations, and prolific authors. Text clustering methods were used to assess technical trends and research hotspots dynamically. The global application status and regulatory framework were also summarized. This analysis illustrates the bottleneck of the GE innovation and provides insights into the future trajectory of development and application of the technology in various fields, which will be helpful for the popularization of gene editing technology.
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Lethal endotoxin (ccdB) based counterselection improved the efficiency of sequential gene editing in Escherichia coli.
The CRISPR/Cas9-based technology has been used for sequential gene editing in E. coli. The plasmids carrying the sgRNA and/or Cas9 genes need to be cured after each round of editing. Curing of these plasmids, particularly the sgRNA plasmid, limits the efficiency of sequential gene editing. In this study, a lethal endotoxin (ccdB) based counterselection was established for improving the overall efficiency of sequential gene editing in E. coli. This approach was validated for sequential editing (deletion) of cstA and ppsA genes in HBUT-P2 strain (W derivative). The experimental results showed that the transformation efficiency of sgRNA plasmid (pTargetF-tcr-PL-ccdB-N20) reached 108-109 cfu/μg-DNA, resulting in a 100% and 93.75% recombination rate for cstA and ppsA gene, respectively. Upon completion of cstA gene editing, the sgRNA plasmid (pTargetF-tcr-PL-ccdB-N20 (cstA)) was effectively cured through ccdB based counterselection at 42 °C, with a 43.75% efficiency. At the end of sequential editing of ppsA gene, both Cas9 (25A) and sgRNA (pTargetF-tcr-PL-ccdB-N20 (ppsA)) plasmids were cured simultaneously through the sacB and ccdB based counterselections by incubating the cells on LB-sucrose (5%) plate at 42 °C, achieving a curing rate of 100% for Cas9 plasmid (25A), 37.5% for sgRNA plasmid (pTargetF-tcr-PL-ccdB-N20 (ppsA)), and 37.5% for both Cas9 and sgRNA plasmids. Moreover, this approach was further validated through efficient site-specific insertion of the csc operon into the slmA gene in DH5α (K12 derivative) and S322 (C derivative) strains. These results demonstrated that the endotoxin (ccdB) based counterselection improved the transformation efficiency of sgRNA plasmid, the recombination rate of the editing target gene, the curing rate of sgRNA plasmid, and the overall efficiency of sequential gene editing.
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Repair of a Site-Specific DNA Cleavage: Old-School Lessons for Cas9-Mediated Gene Editing.
CRISPR/Cas9-mediated gene editing may involve nonhomologous end-joining to create various insertion/deletions (indels) or may employ homologous recombination to modify precisely the target DNA sequence. Our understanding of these processes has been guided by earlier studies using other site-specific endonucleases, both in model organisms such as budding yeast and in mammalian cells. We briefly review what has been gleaned from such studies using the HO and I-SceI endonucleases and how these findings guide current gene editing strategies.
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Guide RNA scaffold variants enabled easy cloning of large gRNA cluster for multiplexed gene editing.
Cas9 protein-mediated gene editing has revolutionized genetic manipulation in most organisms. There are many cases where multiplexed gene editing is needed. Cas9 is capable of multiplex gene editing when expressed with multiple guide RNAs. Conventional cloning methods for multiplexed gene editing vector is not efficient due to repeated use of a single-guide RNA scaffold and inefficient ligation. In this study, we conducted structure-guided mutagenesis and random mutagenesis on the original sgRNA scaffold and identified a large number of functional sgRNA scaffold variants. With these scaffold variants and different tRNAs, fusion polymerase chain reaction protocol was developed to rapidly synthesize spacer-scaffold-tRNA-spacer units with up to 9 targets. In conjunction with golden gate cloning, gene editing vectors with up to 24 target sites were efficiently cloned in one-step cloning. One such gene editing vector targeting 12 genes in tomato were tested in stable transformation and 10 out of the 12 genes were found mutated in a single transgenic line. To facilitate the application of multiplexed gene editing using these scaffold variants and tRNAs from different species, a webserver was created to generate primer sets and provide template sequences for the synthesis of large sgRNA expression units based on the user-supplied target sequences and species.
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Xenotransplantation: Promise, progress, and risks.
Xenotransplantation has seen remarkable progress in recent years, largely driven by the advent of CRISPR-Cas9 gene editing technology. Several patients have received genetically modified kidney and heart transplants, achieving graft and patient survival ranging from days to months. This review offers a brief history of xenotransplantation and highlights advancements in gene editing that represent breakthroughs in minimizing rejection. It also presents recent cases of xenotransplantation and their clinical outcomes. Finally, the review addresses the ethical considerations and risks associated with this emerging field.
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Precision Without Selection: A Marker-Free CRISPR/Cas9-Based Protocol for Multiplexed Genome Editing in Trypanosomatids.
The CRISPR-Cas9 system has become a valuable tool for genome editing in trypanosomatid parasites such as Trypanosoma and Leishmania species. Although these organisms have been genetically engineered for a long time using homologous recombination, CRISPR/Cas9 offers improved efficiency for genome editing. However, conventional strategies employing stable Cas9 expression require the persistent use of a specific genetic background (i.e., strains expressing Cas9), depend on selectable resistance markers, compromise genomic stability, and are not readily applicable to diverse strain backgrounds. Herein, we report an optimized marker-free CRISPR/Cas9 method based on transient ribonucleoprotein (RNP) delivery that overcomes these drawbacks. Our method eliminates the need for plasmid integration or antibiotic selection while maintaining high editing efficiency. The protocol comprises the following steps: (1) design of the guide RNA (gRNA), (2) design of the repair template (cassette), (3) assembly of the ribonucleoprotein (RNP) complex, (4) delivery by electroporation, and (5) clonal screening through PCR and sequencing. The procedure permits rapid (≤3 weeks) production of homozygous mutant lines in wild-type strains, including low-density culture strains. The reproducibility and ease of the technique render it particularly suited for multiplexed editing of polyploid genomes, multi-gene families, and several different genes at once, as well as validation of the essential nature of genes. Although designed for trypanosomatids, the workflow can be adapted to other kinetoplastids, offering a flexible platform for functional genomics.
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Harnessing Gene Editing Technology for Tumor Microenvironment Modulation: An Emerging Anticancer Strategy.
Cancer is a multifaceted disease influenced by both intrinsic cellular traits and extrinsic factors, with the tumor microenvironment (TME) being crucial for cancer progression. To satisfy their high proliferation and aggressiveness, cancer cells always plunder large amounts of nutrients and release various signals to their surroundings, forming a dynamic TME with special metabolic, immune, microbial and physical characteristics. Due to the neglect of interactions between tumor cells and the TME, traditional cancer therapies often struggle with challenges such as drug resistance, low efficacy, and recurrence. Importantly, the development of gene editing technologies, particularly the CRISPR-Cas system, offers promising new strategies for cancer treatment. Combined with nanomaterial strategies, CRISPR-Cas technology exhibits precision, affordability, and user-friendliness with reduced side effects, which holds great promise for profoundly altering the TME at the genetic level, potentially leading to lasting anticancer outcomes. This review will delve into how CRISPR-Cas can be leveraged to manipulate the TME, examining its potential as a transformative anticancer therapy.
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