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Precision in Action: The Role of Clustered Regularly Interspaced Short Palindromic Repeats/Cas in Gene Therapies.
Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-associated enzyme-CAS holds great promise for treating many uncured human diseases and illnesses by precisely correcting harmful point mutations and disrupting disease-causing genes. The recent Food and Drug Association (FDA) approval of the first CRISPR-based gene therapy for sickle cell anemia marks the beginning of a new era in gene editing. However, delivering CRISPR specifically into diseased cells in vivo is a significant challenge and an area of intense research. The identification of new CRISPR/Cas variants, particularly ultra-compact CAS systems with robust gene editing activities, paves the way for the low-capacity delivery vectors to be used in gene therapies. CRISPR/Cas technology has evolved beyond editing DNA to cover a wide spectrum of functionalities, including RNA targeting, disease diagnosis, transcriptional/epigenetic regulation, chromatin imaging, high-throughput screening, and new disease modeling. CRISPR/Cas can be used to engineer B-cells to produce potent antibodies for more effective vaccines and enhance CAR T-cells for the more precise and efficient targeting of tumor cells. However, CRISPR/Cas technology has challenges, including off-target effects, toxicity, immune responses, and inadequate tissue-specific delivery. Overcoming these challenges necessitates the development of a more effective and specific CRISPR/Cas delivery system. This entails strategically utilizing specific gRNAs in conjunction with robust CRISPR/Cas variants to mitigate off-target effects. This review seeks to delve into the intricacies of the CRISPR/Cas mechanism, explore progress in gene therapies, evaluate gene delivery systems, highlight limitations, outline necessary precautions, and scrutinize the ethical considerations associated with its application.
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CRISPR/Cas in gynecologic cancers: A review of experimental and therapeutic applications.
Gynecological malignancies-including cervical, ovarian, and endometrial cancers-remain a major global health challenge, contributing significantly to cancer-related morbidity and mortality among women. Despite advances in conventional treatments such as surgery, chemotherapy, radiotherapy, and immunotherapy, issues such as drug resistance, tumor recurrence, and limited efficacy in advanced-stage disease necessitate novel therapeutic strategies. The emergence of CRISPR/Cas-based genome editing has revolutionized cancer research by enabling precise, efficient, and programmable modifications of specific genomic loci. In gynecologic oncology, CRISPR/Cas systems have been employed to dissect oncogenic mechanisms, identify therapeutic targets, and develop innovative treatment modalities. In cervical cancer, CRISPR-mediated targeting of HPV E6 and E7 oncogenes has shown potential in restoring tumor suppressor pathways and enhancing chemosensitivity. In ovarian cancer, gene editing has been used to modulate chemoresistance, tumor angiogenesis, and metastasis through the knockout of key regulators such as DNMT1, EGFL6, and BRCA1/2. Similarly, in endometrial cancer, CRISPR tools have elucidated mechanisms of hormonal resistance and facilitated the development of in vivo models via somatic gene editing. This review highlights recent advances in the application of CRISPR/Cas technology to gynecologic malignancies, discussing its potential as both a therapeutic and research platform while acknowledging current limitations and translational hurdles.
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Exploration of the pneumocandin biosynthetic gene cluster based on efficient CRISPR/Cas9 gene editing strategy in Glarea lozoyensis.
Pneumocandin B0 (PB0) is a lipopeptide produced by the fungus Glarea lozoyensis. The existing challenges with the low-yield and the extended-fermentation cycle emphasize necessity for strain improvement. In this study, we optimized conditions to obtain high-quality protoplasts and screened effective selection markers, leading to the construction of three CRISPR/Cas9 gene editing systems. Utilizing a constitutive Cas9 expression recipient strain, combined with dual sgRNAs targeting, we achieved highly efficient editing of target genes. We successfully knocked out 10 genes within the pneumocandin putative biosynthetic gene cluster and analyzed their roles in PB0 production. Our findings reveal that 4 of 10 genes are directly involved in PB0 production. Specially, the deletion of gltrt or gl10050 resulted in reduced PB0 production, while the absence of glhyp or glhtyC led to the complete loss of PB0 biosynthesis. Notably, the deletion of glhyp caused the silencing of nearly all cluster genes, whereas overexpression of glhyp led to a 2.38-fold increase in PB0 production. Therefore, this study provides the first comprehensive exploration of the functions of 10 genes within the pneumocandin putative biosynthetic gene cluster. Our findings provide valuable technical strategies for constructing bioengineering strains with purposefully enhanced PB0 production.
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Improving the genome editing efficiency of CRISPR/Cas9 in Arabidopsis and Medicago truncatula.
An improved CRISPR/Cas9 system with the Arabidopsis UBQ10 promoter-driven Cas9 exhibits consistently high mutation efficiency in Arabidopsis and M. truncatula. CRISPR/Cas9 is a powerful genome editing technology that has been applied in several crop species for trait improvement due to its simplicity, versatility, and specificity. However, the mutation efficiency of CRISPR/Cas9 in Arabidopsis and M. truncatula (Mt) is still challenging and inconsistent. To analyze the functionality of the CRISPR/Cas9 system in two model dicot species, four different promoter-driven Cas9 systems to target phytoene desaturase (PDS) genes were designed. Agrobacterium-mediated transformation was used for the delivery of constructed vectors to host plants. Phenotypic and genotypic analyses revealed that the Arabidopsis UBQ10 promoter-driven Cas9 significantly improves the mutation efficiency to 95% in Arabidopsis and 70% in M. truncatula. Moreover, the UBQ10-Cas9 system yielded 11% homozygous mutants in the T1 generation in Arabidopsis. Sequencing analyses of mutation events indicated that single-nucleotide insertions are the most frequent events in Arabidopsis, whereas multi-nucleotide deletions are dominant in bi-allelic and mono-allelic homozygous mutants in M. truncatula. Taken together, the UBQ10 promoter facilitates the best improvement in the CRISPR/Cas9 efficiency in PDS gene editing, followed by the EC1.2 promoter. Consistently, the improved UBQ10-Cas9 vector highly enhanced the mutation efficiency by four-fold over the commonly used 35S promoter in both dicot species.
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Lessons from Domestication: Targeting Cis-Regulatory Elements for Crop Improvement.
Domestication of wild plant species has provided us with crops that serve our human nutritional needs. Advanced DNA sequencing has propelled the unveiling of underlying genetic changes associated with domestication. Interestingly, many changes reside in cis-regulatory elements (CREs) that control the expression of an unmodified coding sequence. Sequence variation in CREs can impact gene expression levels, but also developmental timing and tissue specificity of expression. When genes are involved in multiple pathways or active in several organs and developmental stages CRE modifications are favored in contrast to mutations in coding regions, due to the lack of detrimental pleiotropic effects. Therefore, learning from domestication, we propose that CREs are interesting targets for genome editing to create new alleles for plant breeding.
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An experimental protocol for teaching CRISPR/Cas9 in a post-graduate plant laboratory course: An analysis of mutant-edited plants without sequencing.
The CRISPR/Cas9 system is widely used for editing genes in various organisms and is a very useful tool due to its versatility, simplicity, and efficiency. To teach its principles to post-graduate students we designed a laboratory activity to obtain and analyze PDS3 mutants in Arabidopsis thaliana plants consisting of: 1) Design of guide RNAs using bioinformatics tools; 2) plant transformation (which is optional depending on the length of the course); 3) observation and evaluation of the mutant's phenotypes in the Phytoene desaturase (PDS3) gene, which exhibit an albino phenotype and different degrees of mosaicism in the editing events we evaluated; 4) PCR amplification of a fragment that includes the mutated region followed by analysis of single-stranded DNA conformation polymorphisms (SSCP) using native polyacrylamide gel electrophoresis and silver nitrate staining to detect changes in the amplicon sequence due to gene editing. Through SSCP, the students were able to distinguish between homozygous and heterozygous edited plants. A highlight feature of this protocol is the visualization and detection of the mutation/edition without sequencing the edited fragment.
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Development of a gene-targeting system using CRISPR/Cas9 and utilization of pyrG as a novel selectable marker in Lentinula edodes.
First, we attempted to recombine the Shiitake (Lentinula edodes) pyrG (ura3) gene homologously by introducing a donor vector containing a carboxin resistance gene (lecbxR) flanked by homologous sequences of pyrG into protoplasts of the fungus. However, all the carboxin-resistant transformants only contained ectopic insertions of the exogenous gene and no homologous insertions. Agaricomycetes are generally known for their low efficiency of homologous recombination, and a similar result was shown for L. edodes. We then co-introduced a Cas9 plasmid vector containing a CRISPR/Cas9 expression cassette targeting pyrG and donor plasmid vector. As a result, ∆pyrG strains containing the expected homologous recombination were obtained. However, only two of the seven ∆pyrG strains had the Cas9 sequence; the others did not. Our results suggest that genome editing occurred via the transient expression of the CRISPR/Cas9 cassette in the Cas9 plasmid vector introduced into the fungal cell. Transforming pyrG into a ∆pyrG strain (strain I8) resulted in prototrophic strains with an efficiency of 6.5 strains/experiment.
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CRISPR/Cas9-Mediated triple gene editing of Pi21, Bsr-d1, and Xa5 confers broad-spectrum disease resistance in elite early-season rice without yield compromise.
Rice blast and bacterial blight are devastating diseases that severely threaten global rice production. To develop durable resistance without compromising yield, we utilized CRISPR/Cas9 gene editing to simultaneously knock out three negative immune regulators, Pi21, Bsr-d1, and Xa5, in two elite early-rice cultivars (ZZU53 and ZZU100). We successfully obtained transgene-free homozygous triple mutants that exhibited significantly enhanced resistance to both Magnaporthe oryzae (M. oryzae) and Xanthomonas oryzae pv. oryzae (Xoo). This broad-spectrum resistance correlates with the constitutive upregulation of key defense genes in the salicylic acid (SA) pathway (OsPR1a, OsPR1b, and OsWRKY45) and jasmonic acid (JA) pathways (OsPR4). Comprehensive agronomic evaluation demonstrated that critical agricultural traits such as thousand-grain weight, panicle architecture, heading date, and tiller number remained comparable to wild-type plants, indicating no substantial yield penalty. This approach provides an efficient, transgene-free pathway for developing disease-resistant early-rice cultivars. Multiple environment field trials are now required to evaluate its long-term agricultural viability.
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Use of the Cas9 Orthologs from Streptococcus thermophilus and Staphylococcus aureus for Non-Homologous End-Joining Mediated Site-Specific Mutagenesis in Arabidopsis thaliana.
Since the discovery of the CRISPR/Cas system and its in vivo application for site-specific targeted mutagenesis, this technique is wildly used in a great variety of organisms, such as many plant species. Commonly used for this application is the Cas9 enzyme from Streptococcus pyogenes. Here, we describe the application of two Cas9 orthologs from Streptococcus thermophilus and Staphylococcus aureus for targeted non-homologous end-joining mediated mutagenesis in Arabidopsis thaliana. With both orthologs, we could show efficient inheritance of the induced mutations. As both Cas9 orthologs are smaller in size than the enzyme of S. pyogenes and as the Protospacer adjacent motifs (PAMs) differ between all orthologs, they are attractive alternative tools for genome engineering in plants.
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Robust miniature Cas-based transcriptional modulation by engineering Un1Cas12f1 and tethering Sso7d.
The miniature V-F CRISPR-Cas12f system has been repurposed for gene editing and transcription modulation. The small size of Cas12f satisfies the packaging capacity of adeno-associated virus (AAV) for gene therapy. However, the efficiency of Cas12f-mediated transcriptional activation varies among different target sites. Here, we developed a robust miniature Cas-based transcriptional activation or silencing system using Un1Cas12f1. We engineered Un1Cas12f1 and the cognate guide RNA and generated miniCRa, which led to a 1,319-fold increase in the activation of the ASCL1 gene. The activity can be further increased by tethering DNA-binding protein Sso7d to miniCRa and generating SminiCRa, which reached a 5,628-fold activation of the ASCL1 gene and at least hundreds-fold activation at other genes examined. We adopted these mutations of Un1Cas12f1 for transcriptional repression and generated miniCRi or SminiCRi, which led to the repression of ∼80% on average of eight genes. We generated an all-in-one AAV vector AIOminiCRi used to silence the disease-related gene SERPINA1. AIOminiCRi AAVs led to the 70% repression of the SERPINA1 gene in the Huh-7 cells. In summary, miniCRa, SminiCRa, miniCRi, and SminiCRi are robust miniature transcriptional modulators with high specificity that expand the toolbox for biomedical research and therapeutic applications.
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