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Development of a CRISPR/Cas9-degron system that enables in vivo specific gene depletion in leukemia models.
The CRISPR/Cas9 system has transformed genome editing, yet precise temporal control of Cas9 activity remains challenging. We developed a Cas9-degron platform that couples degron-tagged Cas9 with a dTAG-based chemical degradation strategy. In the presence of dTAG, Cas9 is rapidly and near-completely degraded, preventing editing; upon dTAG withdrawal, Cas9 activity is restored, enabling precise temporal control. Using this system, we achieved selective in vivo gene depletion in acute myeloid leukemia (AML) models and confirmed that SETDB1, a histone H3K9 methyltransferase, is essential for the in vivo growth of both human (MOLM13) and murine (cSAM) AML cells. By maintaining SETDB1 intact prior to transplantation and depleting it afterward, we avoided culture-induced pre-selection bias inherent to sgRNA transduction and validated its critical role in AML progression within the in vivo context. The Cas9-degron retains activity and delivery efficiency comparable to conventional Cas9 in the absence of dTAG. Thus, this versatile system provides a superior alternative to conventional Cas9 and a powerful platform for in vivo CRISPR screening, gene function studies, and potentially temporally controlled gene therapy.
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Generation of RUNX1c-eGFP induced pluripotent stem cell, MUSIi012-A-4, using CRISPR/Cas9.
Runt-Related Transcription Factor 1c (RUNX1c) plays an important role in regulating the development of hematopoietic stem cells (HSC). Using CRISPR/Cas9 gene editing technology, we established a RUNX1c-eGFP reporter cell line from the MUSIi012-A cell line. The MUSIi012-A-4 cell line has normal stem cell morphology and karyotype, expresses pluripotency markers, and can be differentiated into all three germ layers in vitro and in vivo. This cell line serves as a valuable model to observe the expression of RUNX1c via eGFP tracking during human hematopoietic development.
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A boronic acid-rich dendrimer with robust and unprecedented efficiency for cytosolic protein delivery and CRISPR-Cas9 gene editing.
Cytosolic protein delivery is of central importance for the development of protein-based biotechnologies and therapeutics; however, efficient intracellular delivery of native proteins remains a challenge. Here, we reported a boronic acid-rich dendrimer with unprecedented efficiency for cytosolic delivery of native proteins. The dendrimer could bind with both negatively and positively charged proteins and efficiently delivered 13 cargo proteins into the cytosol of living cells. All the delivered proteins kept their bioactivities after cytosolic delivery. The dendrimer ensures efficient intracellular delivery of Cas9 protein into various cell lines and showed high efficiency in CRISPR-Cas9 genome editing. The rationally designed boronic acid-rich dendrimer permits the development of an efficient platform with high generality for the delivery of native proteins.
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Optimization of CRISPR/Cas9-mediated gene disruption in Xenopus laevis using a phenotypic image analysis technique.
The CRISPR/Cas9 method has become popular for gene disruption experiments in Xenopus laevis. However, the experimental conditions that influence the efficiency of CRISPR/Cas9 remain unclear. To that end, we developed an image analysis technique for the semi-quantitative evaluation of the pigment phenotype resulting from the disruption of tyrosinase genes in X. laevis using a CRISPR/Cas9 approach, and then examined the effects of varying five experimental parameters (timing of the CRISPR reagent injection into developing embryos; amount of Cas9 mRNA in the injection reagent; total injection volume per embryo; number of injection sites per embryo; and the culture temperature of the injected embryos) on the gene disruption efficiency. The results of this systematic analysis suggest that the highest possible efficiency of target gene disruption can be achieved by injecting a total of 20 nL of the CRISPR reagent containing 1500 pg of Cas9 mRNA or 4 ng of Cas9 protein into two separate locations (10 nL each) of one-cell stage embryos cultured at 22°C. This study also highlights the importance of balancing the experimental parameters for increasing gene disruption efficiency and provides valuable insights into the optimal conditions for applying the CRISPR/Cas9 system to new experimental organisms.
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Progress in Gene Editing and Metabolic Regulation of Saccharomyces cerevisiae with CRISPR/Cas9 Tools.
The CRISPR/Cas9 systems have been developed as tools for genetic engineering and metabolic engineering in various organisms. In this review, various aspects of CRISPR/Cas9 in Saccharomyces cerevisiae, from basic principles to practical applications, have been summarized. First, a comprehensive review has been conducted on the history of CRISPR/Cas9, successful cases of gene disruptions, and efficiencies of multiple DNA fragment insertions. Such advanced systems have accelerated the development of microbial engineering by reducing time and labor, and have enhanced the understanding of molecular genetics. Furthermore, the research progress of the CRISPR/Cas9-based systems in the production of high-value-added chemicals and the improvement of stress tolerance in S. cerevisiae have been summarized, which should have an important reference value for genetic and synthetic biology studies based on S. cerevisiae.
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Key considerations in designing CRISPR/Cas9-carrying nanoparticles for therapeutic genome editing.
CRISPR-Cas9, the breakthrough genome-editing technology, has emerged as a promising tool to prevent and cure various diseases. The efficient genome editing technology strongly relies on the specific and effective delivery of CRISPR/Cas9 cargos. However, the lack of a safe, specific, and efficient non-viral delivery system for in vivo genome editing remains a major limit for its clinical translation. In this review, we will first briefly introduce the working mechanism of CRISPR/Cas9 and the patterns of CRISPR/Cas9 delivery. Furthermore, the physiological obstacles for the delivery process in vivo are elaborated. Finally, the key considerations will be deeply discussed in designing non-viral nanovectors for therapeutic CRISPR/Cas9 delivery in vivo, including the effective encapsulation of large-size macromolecules, targeting specific tissues and cells, efficient endosomal escape and safety concerns of the vector systems, in the hope of inviting more comprehensive studies on the development of safe, specific, and efficient non-viral nanovectors for delivering a CRISPR/Cas9 system.
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CRISPR-Cas Systems Reduced to a Minimum.
In two recent studies in Molecular Cell, Wright et al. (2019) report complete spacer integration by a Cas1 mini-integrase and Edraki et al. (2019) describe accurate genome editing by a small Cas9 ortholog with less stringent PAM requirements.
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Genetical engineering for NK and T cell immunotherapy with CRISPR/Cas9 technology: Implications and challenges.
Immunotherapy has become one of the most promising strategies in cancer therapies. Among the therapeutic alternatives, genetically engineered NK/T cell therapies have emerged as powerful and innovative therapeutic modalities for cancer patients with precise targeting and impressive efficacy. Nonetheless, this approach still faces multiple challenges, such as immunosuppressive tumor microenvironment, exhaustion of immune effector cells in tumors, off-target effects manufacturing complexity, and poor infiltration of effector cells, all of which need to be overcome for further utilization to cancers. Recently, CRISPR/Cas9 genome editing technology, with the goal of enhancing the efficacy and increasing the availability of engineered effector cell therapies, has shown considerable potential in the novel strategies and options to overcome these limitations. Here we review the current progress of the applications of CRISPR in cancer immunotherapy. Furthermore, we discuss issues related to the NK/T cell applications, gene delivery methods, efficiency, challenges, and implications of CRISPR/Cas9.
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Reduction of Pre-Existing Adaptive Immune Responses Against SaCas9 in Humans Using Epitope Mapping and Identification.
The CRISPR-Cas9 system is increasingly being used as a gene editing therapeutic technique in complex diseases but concerns remain regarding the clinical risks of Cas9 immunogenicity. In this study, we detected antibodies against Staphylococcus aureus Cas9 (SaCas9) and anti-SaCas9 T cells in 4.8% and 70% of Chinese donors, respectively. We predicted 135 SaCas9-derived B cell epitopes and 50 SaCas9-derived CD8+ T cell epitopes for HLA-A*24:02, HLA-A*11:01, and HLA-A*02:01. We identified R338 as an immunodominant SaCas9 B cell epitope and SaCas9_200-208 as an immunodominant CD8+ T cell epitope for the three human leukocyte antigen allotypes through immunological assays using sera positive for SaCas9-specific antibodies and peripheral blood mononuclear cells positive for SaCas9-reactive T cells, respectively. We also demonstrated that an SaCas9 variant bearing an R338G substitution reduces B cell immunogenicity and retains its gene-editing function. Our study highlights the immunological risks of the CRISPR-Cas9 system and provides a solution to mitigate pre-existing adaptive immune responses against Cas9 in humans.
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Co-Delivery of Multiple RNAs via Lipid Nanoparticles Enables Precise Gene Editing of CAR-T Cells.
Over the past decade, CAR-T cell therapy has achieved remarkable success in treating hematological malignancies. However, traditional CAR-T cell engineering employs viral vectors, which has several limitations. Additionally, the immunosuppressive tumor microenvironment, particularly mediated by the PD-1/PD-L1 pathway, significantly restricts CAR-T cell efficacy. CRISPR/Cas9-mediated PD-1 knockout can enhance CAR-T cell anti-tumor activity, but traditional electroporation (EP) method often damages T cells. Herein, a novel lipid nanoparticles (LNPs)-mediated delivery technology are introduced to engineer CAR-T cells. The LNPs platform enables the simultaneous expression of CAR cassette and CRISPR/Cas9 gene editor in T cells via co-delivery of multiplex RNAs (CD19 CAR mRNA+Cas9 mRNA+sgRNA targeting PD-1). Importantly, LNPs exhibit higher transfection efficiency and superior cell viability compared to traditional electroporation method. The engineered CAR-T cells with PD-1 knockout, which express anti-CD19 CAR, can specifically kill CD19+ Nalm-6 tumor cells in vitro and display enhanced anti-tumor activity in vivo. Furthermore, LNPs-mediated co-delivery of Cas9 mRNA and sgRNAs targeting PD-1, TRAC, and B2M enables triple-knockout of T cells with high editing efficiencies (76% for PD-1, 86% for TRAC, and 80% for B2M), highlighting the ability for multiplex gene editing. This LNP-mediated delivery strategy has great potentials for the development of safer and more efficacious CAR-T cells.
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