Comprehensive review of CRISPR-based gene editing: mechanisms, challenges, and applications in cancer therapy.

The CRISPR system is a revolutionary genome editing tool that has the potential to revolutionize the field of cancer research and therapy. The ability to precisely target and edit specific genetic mutations that drive the growth and spread of tumors has opened up new possibilities for the development of more effective and personalized cancer treatments. In this review, we will discuss the different CRISPR-based strategies that have been proposed for cancer therapy, including inactivating genes that drive tumor growth, enhancing the immune response to cancer cells, repairing genetic mutations that cause cancer, and delivering cancer-killing molecules directly to tumor cells. We will also summarize the current state of preclinical studies and clinical trials of CRISPR-based cancer therapy, highlighting the most promising results and the challenges that still need to be overcome. Safety and delivery are also important challenges for CRISPR-based cancer therapy to become a viable clinical option. We will discuss the challenges and limitations that need to be overcome, such as off-target effects, safety, and delivery to the tumor site. Finally, we will provide an overview of the current challenges and opportunities in the field of CRISPR-based cancer therapy and discuss future directions for research and development. The CRISPR system has the potential to change the landscape of cancer research, and this review aims to provide an overview of the current state of the field and the challenges that need to be overcome to realize this potential.

ExsgRNA: reduce off-target efficiency by on-target mismatched sgRNA.

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing technology has been widely used to facilitate efficient genome editing. Current popular sgRNA design tools only consider the sgRNA perfectly matched to the target site and provide the results without any on-target mismatch. We suppose taking on-target gRNA-DNA mismatches into consideration might provide better sgRNA with similar binding activity and reduced off-target sites. Here, we trained a seq2seq-attention model with feedback-loop architecture, to automatically generate sgRNAs with on-target mismatches. Dual-luciferase reporter experiment showed that multiple sgRNAs with three mismatches could achieve the 80% of the relative activity of the perfect matched sgRNA. Meanwhile, it could reduce the number of off-target sites using sgRNAs with on-target mismatches. Finally, we provided a freely accessible web server sgRNA design tool named ExsgRNA. Users could submit their target sequence to this server and get optimal sgRNAs with less off-targets and similar on-target activity compared with the perfect-matched sgRNA.

Genome editing tools based improved applications in macrofungi.

Macrofungi commonly referred to as Mushrooms are distributed worldwide and well known for their nutritional, medicinal, and organoleptic properties. Strain improvement in mushrooms is lagging due to paucity of efficient genome modification techniques. Thus, for advanced developments in research and commercial or economical viability and benefit, CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9) emerged as an efficient genome editing tool. The higher efficiency and precision of the desired genetic modification(s) are the most valuable attributes of this recent technology. The present review comprehensively summarizes various conventional methods utilized for strain improvement in mushrooms including hybridization, protoplast fusion, and di-mon mating. Furthermore, the problems associated with these techniques have been discussed besides providing the potential recluses. The significance of CRISPR/Cas9 strategies employed for improvement in various mushroom genera has been deliberated, as these strategies will paves the way forward for obtaining improved strain and effective cultivation methods for enhancing the yield and quality of the fruit bodies.

Short cell-penetration peptide conjugated bioreducible polymer enhances gene editing of CRISPR system.

CRISPR-based gene therapy offers precise targeting and specific editing of disease-related gene sequences, potentially yielding long-lasting treatment effects. However, efficient delivery remains a significant challenge for its widespread application. In this study, we design a novel short peptide-conjugated bioreducible polymer named TSPscp as a safe and effective delivery vector for the CRISPR system. Our results show that TSPscp markedly boosts transcriptional activation and genome editing activities of multiple CRISPR systems as confirmed by decomposition-seq and Deep-seq, which is resulted from its capability in facilitating delivery of plasmid DNA by promoting cellular uptake and lysosomal escape. Additionally, TSPscp further enhances genome editing of CRISPR by delivery of minicircle DNA, a condensed form of regular plasmid DNA. More importantly, TSPscp significantly improves delivery and genome editing of CRISPR system in vivo. In summary, our study highlights TSPscp as a promising delivery tool for CRISPR applications in vivo.

CRISPR-based gene expression platform for precise regulation of bladder cancer.

The development of compact CRISPR systems has facilitated delivery but has concurrently reduced gene editing efficiency, thereby limiting the further utilization of CRISPR systems. Enhancing the efficiency of CRISPR systems poses a challenging task and holds significant implications for the advancement of biotechnology. In our work, we report a synthetic dual-antibody system that can stably exist in the intracellular environment, specifically inhibiting the functions of NF-κB and ß-catenin. This not only elevates the transgenic expression of the CRISPR system by suppressing the innate immune response within cells to enhance the gene editing efficiency but also demonstrates a notable tumor inhibitory effect. Based on the specific output expression regulation of CRISPR-CasΦ, we constructed a CRISPR-based gene expression platform, which includes sensor modules for detecting intracellular ß-catenin and NF-κB, as well as an SDA module to enhance overall efficiency. In vitro experiments revealed that the CRISPR-based gene expression platform exhibited superior CDK5 expression inhibition efficiency and specific cytotoxicity towards tumor cells. In vitro experiments, we found that CRISPR-based gene expression platforms can selectively kill bladder cancer cells through T cell-mediated cytotoxicity. Our design holds significant assistant potential of transgene therapy and may offer the capability to treat other diseases requiring transgene therapy.

Targeted large fragment deletion in plants using paired crRNAs with type I CRISPR system.

The CRISPR-Cas systems have been widely used as genome editing tools, with type II and V systems typically introducing small indels, and type I system mediating long-range deletions. However, the precision of type I systems for large fragment deletion is still remained to be optimized. Here, we developed a compact Cascade-Cas3 Dvu I-C system with Cas11c for plant genome editing. The Dvu I-C system was efficient to introduce controllable large fragment deletion up to at least 20 kb using paired crRNAs. The paired-crRNAs design also improved the controllability of deletions for the type I-E system. Dvu I-C system was sensitive to spacer length and mismatch, which was benefit for target specificity. In addition, we showed that the Dvu I-C system was efficient for generating stable transgenic lines in maize and rice with the editing efficiency up to 86.67%. Overall, Dvu I-C system we developed here is powerful for achieving controllable large fragment deletions.

Reprogramming Targeted-Antibacterial-Plasmids (TAPs) to achieve broad-host range antibacterial activity.

The emergence and spread of antimicrobial resistance results in antibiotic inefficiency against multidrug resistant bacterial strains. Alternative treatment to antibiotics must be investigated to fight bacterial infections and limit this global public health problem. We recently developed an innovative strategy based on mobilizable Targeted-Antibacterial-Plasmids (TAPs) that deliver CRISPR/Cas systems with strain-specific antibacterial activity, using the F plasmid conjugation machinery for transfer into the targeted strains. These TAPs were shown to specifically kill a variety of Enterobacteriaceae strains, including E. coli K12 and the pathogen strains EPEC, Enterobacter cloacae and Citrobacter rodentium. Here, we extend the host-range of TAPs using the RP4 plasmid conjugation system for their mobilization, thus allowing the targeting of E. coli but also phylogenetically distant species, including Salmonella enterica Thyphimurium, Klebsiella pneumoniae, Vibrio cholerae, and Pseudomonas aeruginosa. This work demonstrates the versatility of the TAP strategy and represents a significant step toward the development of non-antibiotic strain-specific antimicrobial treatments.

Tolerance of Sulfolobus SMV1 virus to the immunity of I-A and III-B CRISPR-Cas systems in Sulfolobus islandicus.

Sulfolobus islandicus Rey15A encodes one Type I-A and two Type III-B systems, all of which are active in mediating nucleic acids interference. However, the effectiveness of each CRISPR system against virus infection was not tested in this archaeon. Here we constructed S. islandicus strains that constitutively express the antiviral immunity from either I-A, or III-B, or I-A plus III-B systems against SMV1 and tested the response of each host to SMV1 infection. We found that, although both CRISPR immunities showed a strong inhibition to viral DNA replication at an early stage of incubation, the host I-A CRISPR immunity gradually lost the control on virus proliferation, allowing accumulation of cellular viral DNA and release of a large number of viral particles. In contrast, the III-B CRISPR immunity showed a tight control on both viral DNA replication and virus particle formation. Furthermore, the SMV1 tolerance to the I-A CRISPR immunity did not result from the occurrence of escape mutations, suggesting the virus probably encodes an anti-CRISPR protein (Acr) to compromise the host I-A CRISPR immunity. Together, this suggests that the interplay between viral Acrs and CRISPR-Cas systems in thermophilic archaea could have shaped the stable virus-host relationship that is observed for many archaeal viruses.

CRISPR system in the yeast Saccharomyces cerevisiae and its application in the bioproduction of useful chemicals.

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) immune systems in bacteria have been used as tools for genome engineering. Thus far, the CRISPR-Cas system has been used in various yeast, bacterial, and mammalian cells. Saccharomyces cerevisiae is a nonpathogenic yeast, classified under "generally recognized as safe", and has long been used to produce consumables such as alcohol or bread. Additionally, recombinant cells of S. cerevisiae have been constructed and used to produce various bio-based chemicals. Some types of CRISPR-Cas system for genetic manipulation have been constructed during the early developmental stages of the CRISPR-Cas system and have been mainly used for gene knock-in and knock-out manipulations. Thereafter, these systems have been used for various novel purposes such as metabolic engineering and tolerance engineering. In this review, we have summarized different aspects of the CRISPR-Cas in the yeast S. cerevisiae, from its basic principles to various applications. This review describes the CRISPR system in S. cerevisiae based on the differences in its origin and efficiency followed by its basic applications; for example, its involvement in gene knock-in and knock-out has been outlined. Finally, advanced applications of the CRISPR system in the bioproduction of useful chemicals have been summarized.

A highly efficient method for genomic deletion across diverse lengths in thermophilic Parageobacillus thermoglucosidasius.

Parageobacillus thermoglucosidasius is emerging as a highly promising thermophilic organism for metabolic engineering. The utilization of CRISPR-Cas technologies has facilitated programmable genetic manipulation in P. thermoglucosidasius. However, the absence of thermostable NHEJ enzymes limited the capability of the endogenous type I CRISPR-Cas system to generate a variety of extensive genomic deletions. Here, two thermophilic NHEJ enzymes were identified and combined with the endogenous type I CRISPR-Cas system to develop a genetic manipulation tool that can achieve long-range genomic deletion across various lengths. By optimizing this tool-through adjusting the expression level of NHEJ enzymes and leveraging our discovery of a negative correlation between GC content of the guide RNA (gRNA) and deletion efficacy-we streamlined a comprehensive gRNA selection manual for whole-genome editing, achieving a 100 % success rate in randomly selecting gRNAs. Notably, using just one gRNA, we achieved genomic deletions spanning diverse length, exceeding 200 kilobases. This tool will facilitate the genomic manipulation of P. thermoglucosidasius for both fundamental research and applied engineering studies, further unlocking its potential as a thermophilic cell factory.

Targeted DNA Methylation Editing Using an All-in-One System Establishes Paradoxical Activation of EBF3.

Cutaneous melanoma is rapidly on the rise globally, surpassing the growth rate of other cancers, with metastasis being the primary cause of death in melanoma patients. Consequently, understanding the mechanisms behind this metastatic process and exploring innovative treatments is of paramount importance. Recent research has shown promise in unravelling the role of epigenetic factors in melanoma progression to metastasis. While DNA hypermethylation at gene promoters typically suppresses gene expression, we have contributed to establishing the newly understood mechanism of paradoxical activation of genes via DNA methylation, where high methylation coincides with increased gene activity. This mechanism challenges the conventional paradigm that promoter methylation solely silences genes, suggesting that, for specific genes, it might actually activate them. Traditionally, altering DNA methylation in vitro has involved using global demethylating agents, which is insufficient for studying the mechanism and testing the direct consequence of gene methylation changes. To investigate promoter hypermethylation and its association with gene activation, we employed a novel approach utilising a CRISPR-SunTag All-in-one system. Here, we focused on editing the DNA methylation of a specific gene promoter segment (EBF3) in melanoma cells using the All-in-one system. Using bisulfite sequencing and qPCR with RNA-Seq, we successfully demonstrated highly effective methylation and demethylation of the EBF3 promoter, with subsequent gene expression changes, to establish and validate the paradoxical role of DNA methylation. Further, our study provides novel insights into the function of the EBF3 gene, which remains largely unknown. Overall, this study challenges the conventional view of methylation as solely a gene-silencing mechanism and demonstrates a potential function of EBF3 in IFN pathway signalling, potentially uncovering new insights into epigenetic drivers of malignancy and metastasis.

Optimizing Rice Genomics: Employing the Hypercompact Cas12j2 System for Targeted Transcriptional Regulation and Epigenome Modification.

In the burgeoning field of genome engineering, the CRISPR-Cas systems have emerged as pivotal tools for precise genetic modifications in various organisms, including humans, animals, and plants. One significant obstacle in this arena is the substantial size of Cas proteins, such as SpCas9, which is approximately 190 kDa, complicating their delivery, particularly via viral vectors. To overcome this challenge, our research introduces the hypercompact Cas12j2 system, a groundbreaking development with a size of merely ~80 kDa, originally identified in Biggiephage. We demonstrate its application in plant genome editing, with a particular focus on rice. In this context, we have successfully adapted Cas12j2 for gene activation, achieving significant increases in gene expression, specifically up to a tenfold activation for OsER1 and a fourfold activation for OsNRT1.1A in stable transgenic rice plants. Moreover, we have ventured beyond mere gene editing to develop a Cas12j2-based approach for targeted epigenome editing, particularly in the context of DNA methylation. This was demonstrated through the targeted methylation of the OsGBSS1 promoter, as verified by Next-Generation Sequencing of bisulfite sequencing PCR products. This chapter presents a detailed protocol about utilizing the hypercompact Cas12j2 system in conjunction with specific effectors, such as transcriptional activation or repression domains, or methylation domains, to achieve targeted gene transcriptional regulation and epigenome modification in rice.

Remodeling Tumor Immunogenicity with Dual-Activatable Binary CRISPR Nanomedicine for Cancer Immunotherapy.

The specific recognition of cancer cells by the body's immune system is an essential step in initiating antitumor immunity. However, the decreased expression of major histocompatibility complex class I (MHC-1) and overexpression of programmed death ligand 1 (PD-L1) causes insufficient tumor-associated antigens presentation and inactivation of T cells, which accounts for poor immunogenicity. To remodel tumor immunogenicity, herein, a dual-activatable binary CRISPR nanomedicine (DBCN) that can efficiently deliver a CRISPR system into tumor tissues and specifically control its activation is reported. This DBCN is made of a thioketal-cross-linked polyplex core and an acid-detachable polymer shell, which can maintain stability during blood circulation, while detaching a polymer shell to facilitate the cellular internalization of the CRISPR system after entering tumor tissues and ultimately activating gene editing under exogenous laser irradiation, thereby maximizing the therapeutic benefits and reducing potential safety concerns. With the collaborative application of multiple CRISPR systems, DBCN efficiently corrects both dysregulation of MHC-1 and PD-L1 expression in tumors, thus initiating robust T cell-dependent antitumor immune responses to inhibit malignant tumor growth, metastasis, and recurrence. Given the increasing abundance of CRISPR toolkits, this research provides an appealing therapeutic strategy and a universal delivery platform to develop more advanced CRISPR-based cancer treatments.

Common strategies in silkworm disease resistance breeding research.

The silkworm, which is considered a model invertebrate organism, was the first insect used for silk production in human history and has been utilized extensively throughout its domestication. However, sericulture has been plagued by various pathogens that have  caused significant economic losses. To enhance the resistance of a host to its pathogens,numerous strategies have been developed. For instance, gene-editing techniques have been applied to a wide range of organisms, effectively solving a variety of experimental problems. This review focuses on several common silkworm pests and their pathogenic mechanisms, with a particular emphasis on breeding for disease resistance to control multiple types of silkworm diseases. The review also compares the advantages and disadvantages of transgenic technology and gene-editing systems. Finally, the paper provides a brief summary of current strategies used in breeding silkworm disease resistance, along with a discussion of the establishment of existing technologies and their future application prospects. © 2023 Society of Chemical Industry.

Establishment of a Novel Detection Platform for Clostridioides difficile Toxin Genes Based on Orthogonal CRISPR.

Clostridioides difficile is one of the leading pathogens causing nosocomial infection. The infection can range from mild to severe, and rapid identification is pivotal for early clinical diagnosis and appropriate treatment. Here, a genetic testing platform for toxins, referred to as OC-MAB (orthogonal CRISPR system combined with multiple recombinase polymerase amplification [RPA]), was developed to detect the C. difficile toxin genes tcdA and tcdB. While recognizing the amplified products of the tcdA gene and the tcdB gene, Cas13a and Cas12a could activate their cleavage activities to cut labeled RNA and DNA probes, respectively. The cleaved products were subsequently identified by dual-channel fluorescence using a quantitative PCR (qPCR) instrument. Finally, they could also be combined with labeled antibodies on immunochromatographic test strips to achieve visual detection. The OC-MAB platform exhibited ultrahigh sensitivity in detecting the tcdA and tcdB genes at levels of as low as 102 to 101 copies/mL. When testing 72 clinical stool samples, the sensitivity (95% confidence interval [CI], 0.90, 1) and specificity (95% CI, 0.84, 1) of the single-tube method based on the fluorescence readout was 100%, with a positive predictive value (PPA) value of 100% (95% CI, 0.90, 1) and a negative predictive value (NPA) value of 100% (95% CI, 0.84, 1), compared to the results of qPCR. Likewise, the sensitivity of the 2-step method based on the test strip readout was 100% (95% CI, 0.90, 1), while the specificity was 96.3% (95% CI, 0.79, 0.99), with a PPA of 98% (95% CI, 0.87, 0.99) and an NPA of 100% (95% CI, 0.90, 1). In short, orthogonal CRISPR technology is a promising tool for the detection of C. difficile toxin genes. IMPORTANCE C. difficile is currently the primary causative agent of hospital-acquired antibiotic-induced diarrhea, and timely and accurate diagnosis is crucial for hospital-acquired infection control and epidemiological investigation. Here, a new method for the identification of C. difficile was developed based on the recently popular CRISPR technology, and an orthogonal CRISPR dual system was utilized for the simultaneous detection of toxin genes A and B. It also uses a currently rare CRISPR dual-target lateral flow strip with powerful color-changing capabilities, which is appropriate for point-of-care testing (POCT).

CRISPR-based m6A modification and its potential applications in telomerase regulation.

Telomerase determines cell lifespan by controlling chromosome stability and cell viability, m6A epigenetic modification plays an important role in the regulation of telomerase activity. Using CRISPR epigenome editing to analyze specific m6A modification sites in telomerase will provide an important tool for analyzing the molecular mechanism of m6A modification regulating telomerase activity. In this review, we clarified the relevant applications of CRISPR system, paid special attention to the regulation of m6A modification in stem cells and cancer cells based on CRISPR system, emphasized the regulation of m6A modification on telomerase activity, pointed out that m6A modification sites regulate telomerase activity, and discussed strategies based on telomerase activity and disease treatment, which are helpful to promote the research of anti-aging and tumor related diseases.

Application of the endogenous CRISPR-Cas type I-D system for genetic engineering in the thermoacidophilic archaeon Sulfolobus acidocaldarius.

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas systems are widely distributed among bacteria and archaea. In this study, we demonstrate the successful utilization of the type I-D CRISPR-Cas system for genetic engineering in the thermoacidophilic archaeon Sulfolobus acidocaldarius. Given its extreme growth conditions characterized by a temperature of 75°C and pH 3, an uracil auxotrophic selection system was previously established, providing a basis for our investigations. We developed a novel plasmid specifically designed for genome editing, which incorporates a mini-CRISPR array that can be induced using xylose, resulting in targeted DNA cleavage. Additionally, we integrated a gene encoding the ß-galactosidase of Saccharolobus solfataricus into the plasmid, enabling blue-white screening and facilitating the mutant screening process. Through the introduction of donor DNA containing genomic modifications into the plasmid, we successfully generated deletion mutants and point mutations in the genome of S. acidocaldarius. Exploiting the PAM (protospacer adjacent motif) dependence of type I systems, we experimentally confirmed the functionality of three different PAMs (CCA, GTA, and TCA) through a self-targeting assessment assay and the gene deletion of upsE. Our findings elucidate the application of the endogenous Type I-D CRISPR-Cas system for genetic engineering in S. acidocaldarius, thus expanding its genetic toolbox.

Bioinformatic survey of CRISPR loci across 15 Serratia species.

The Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins (CRISPR-Cas) system of prokaryotes is an adaptative immune defense mechanism to protect themselves from invading genetic elements (e.g., phages and plasmids). Studies that describe the genetic organization of these prokaryotic systems have mainly reported on the Enterobacteriaceae family (now reorganized within the order of Enterobacterales). For some genera, data on CRISPR-Cas systems remain poor, as in the case of Serratia (now part of the Yersiniaceae family) where data are limited to a few genomes of the species marcescens. This study describes the detection, in silico, of CRISPR loci in 146 Serratia complete genomes and 336 high-quality assemblies available for the species ficaria, fonticola, grimesii, inhibens, liquefaciens, marcescens, nematodiphila, odorifera, oryzae, plymuthica, proteomaculans, quinivorans, rubidaea, symbiotica, and ureilytica. Apart from subtypes I-E and I-F1 which had previously been identified in marcescens, we report that of I-C and the I-E unique locus 1, I-E*, and I-F1 unique locus 1. Analysis of the genomic contexts for CRISPR loci revealed mdtN-phnP as the region mostly shared (grimesii, inhibens, marcescens, nematodiphila, plymuthica, rubidaea, and Serratia sp.). Three new contexts detected in genomes of rubidaea and fonticola (puu genes-mnmA) and rubidaea (osmE-soxG and ampC-yebZ) were also found. The plasmid and/or phage origin of spacers was also established.

Improving recombinant protein production in CHO cells using the CRISPR-Cas system.

Chinese hamster ovary (CHO) cells are among the most widely used mammalian cell lines in the biopharmaceutical industry. Therefore, it is not surprising that significant efforts have been made around the engineering of CHO cells using genetic engineering methods such as the CRISPR-Cas system. In this review, we summarize key recent studies that have used different CRISPR-Cas systems such as Cas9, Cas13 or dCas9 fused with effector domains to improve recombinant protein (r-protein) production in CHO cells. Here, every relevant stage of production was considered, underscoring the advantages and limitations of these systems, as well as discussing their bottlenecks and probable solutions. A special emphasis was given on how these systems could disrupt and/or regulate genes related to glycan composition, which has relevant effects over r-protein properties and in vivo activity. Furthermore, the related promising future applications of CRISPR to achieve a tunable, reversible, or highly stable editing of CHO cells are discussed. Overall, the studies covered in this review show that despite the complexity of mammalian cells, the synthetic biology community has developed many mature strategies to improve r-protein production using CHO cells. In this regard, CRISPR-Cas technology clearly provides efficient and flexible genetic manipulation and allows for the generation of more productive CHO cell lines, leading to more cost-efficient production of biopharmaceuticals, however, there is still a need for many emerging techniques in CRISPR to be reported in CHO cells; therefore, more research in these cells is needed to realize the full potential of this technology.

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.