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Lentivirus pre-packed with Cas9 protein for safer gene editing.
The CRISPR/Cas9 system provides an easy way to edit specific site/s in the genome and thus offers tremendous opportunity for human gene therapy for a wide range of diseases. However, one major concern is off-target effects, particularly with long-term expression of Cas9 nuclease when traditional expression methods such as via plasmid/viral vectors are used. To overcome this limitation, we pre-packaged Cas9 protein (Cas9P LV) in lentiviral particles for transient exposure and showed its effectiveness for gene disruption in cells, including primary T cells expressing specific single guide RNAs (sgRNAs). We then constructed an 'all in one virus' to express sgRNAs in association with pre-packaged Cas9 protein (sgRNA/Cas9P LV). We successfully edited CCR5 in TZM-bl cells by this approach. Using an sgRNA-targeting HIV long terminal repeat, we also were able to disrupt HIV provirus in the J-LAT model of viral latency. Moreover, we also found that pre-packaging Cas9 protein in LV particle reduced off-target editing of chromosome 4:-29134166 locus by CCR5 sgRNA, compared with continued expression from the vector. These results show that sgRNA/Cas9P LV can be used as a safer approach for human gene therapy applications.
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Generation of a human induced pluripotent stem cell line with Cas9 driven by Tet-on operator via AAVS1 safe harbor gene-editing.
Human induced pluripotent stem (iPS) cells expressing Cas9 protein are valuable for the pathogenic mechanism study and drug discovery. These cells can be efficiently induced to differentiate into disease cell models with specific mutations through adding designed sgRNAs. Here, we generated a human gene-editable iPS cell line by gene editing method that Cas9 gene driven by Tet-on operator was perfectly integrated into the human AAVS1 safe harbor locus. The established Cas9 expression iPS cell line named as WMUi013-A can express endogenous pluripotent markers, has the ability to differentiate into the three germ layers, and possesses a normal karyotype.
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Generation of Efficient Knock-in Mouse and Human Pluripotent Stem Cells Using CRISPR-Cas9.
A knock-in can generate fluorescent or Cre-reporter under the control of an endogenous promoter. It also generates knock-out or tagged-protein with fluorescent protein and short tags for tracking and purification. Recent advances in genome editing with clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated protein 9 (Cas9) significantly increased the efficiencies of making knock-in cells. Here we describe the detailed protocols of generating knock-in mouse and human pluripotent stem cells (PSCs) by electroporation and lipofection, respectively.
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Engineering a robust Cas12i3 variant-mediated wheat genome editing system.
Wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) is one of the most important food crops in the world. CRISPR/Cas12i3, which belongs to the type V-I Cas system, has attracted extensive attention recently due to its smaller protein size and its less-restricted canonical 'TTN' protospacer adjacent motif (PAM). However, due to its relatively lower editing efficacy in plants and the hexaploidy complex nature of wheat, Cas12i3/Cas12i3-5M-mediated genome editing in wheat has not been documented yet. Here, we report the engineering of a robust Cas12i3-5M-mediated genome editing system in wheat through the fusion of T5 exonuclease (T5E) in combination with an optimised crRNA expression strategy (Opt). We first showed that fusion of T5E, rather than ExoI, to Cas12i3-5M increased the gene editing efficiencies by up to 1.34-fold and 3.87-fold, compared to Cas12i3-5M and Cas12i3 in HEK293T cells, respectively. However, its editing efficiency remains low in wheat. We then optimised the crRNA expression strategy and demonstrated that Opt-T5E-Cas12i3-5M could enhance the editing efficiency by 1.20- to 1.33-fold and 4.05- to 7.95-fold in wheat stable lines compared to Opt-Cas12i3-5M and Opt-Cas12i3, respectively, due to progressive 5'-end resection of the DNA strand at the cleavage site with increased deletion size. The Opt-T5E-Cas12i3-5M enabled an editing efficiency ranging from 60.71% to 90.00% across four endogenous target genes in stable lines of three elite Chinese wheat varieties. Together, the developed robust Opt-T5E-Cas12i3-5M system enriches wheat genome editing toolkits for either biological research or genetic improvement and may be extended to other important polyploidy crop species.
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What's in a cure: designing a broad-spectrum HIV gene therapy.
PURPOSE OF REVIEW: The leading gene editing strategy for a human immunodeficiency virus type 1 (HIV-1) cure involves the delivery of SaCas9 and two guide RNAs (gRNAs) in an adeno-associated viral (AAV) vector. As a dual-component system, CRISPR is targeted to a genetic locus through the choice of a Cas effector and gRNA protospacer design pair. As CRISPR research has expanded in recent years, these components have been investigated for utilization in cure strategies, which will be discussed in this article. RECENT FINDINGS: Type II SpCas9 and SaCas9 have been the leading Cas effectors across gene editing therapeutics to date. Additionally, extensive research has expanded the potential to multiplex gRNAs and target them effectively to the highly genetically diverse HIV-1 provirus. More recently, the Type V family of Cas12 effectors opens a new opportunity to use a smaller Cas protein for packaging into an AAV vector with multiplexed gRNAs. SUMMARY: In understanding the individual components of a CRISPR/Cas therapeutic cure for HIV-1, it is important to know that the currently used strategies can be improved upon. Future areas will include alternative smaller Cas effectors, multiplexed gRNAs designs, and/or alternative delivery modalities.
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Use of CRISPR-Cas tools to engineer Trichoderma species.
Given their lignocellulose degradability and biocontrol activities, fungi of the ubiquitously distributed genus Trichoderma have multiple industrial and agricultural applications. Genetic manipulation plays a valuable role in tailoring novel engineered strains with enhanced target traits. Nevertheless, as applied to fungi, the classic tools of genetic manipulation tend to be time-consuming and tedious. However, the recent development of the CRISPR-Cas system for gene editing has enabled researchers to achieve genome-wide gene disruptions, gene replacements, and precise editing, and this technology has emerged as a primary focus for novel developments in engineered strains of Trichoderma. Here, we provide a brief overview of the traditional approaches to genetic manipulation, the different strategies employed in establishing CRSIPR-Cas systems, the utilization of these systems to develop engineered strains of Trichoderma for desired applications, and the future trends in biotechnology.
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Recombineering in Staphylococcus aureus.
Recombineering has proven to be an extraordinarily powerful and versatile approach for the modification of bacterial genomes, but has historically not been possible in the important opportunistic pathogen Staphylococcus aureus. After evaluating the activity of various recombinases in S. aureus, we developed methods for recombineering in that organism using synthetic, single-stranded DNA oligonucleotides. This approach can be coupled to CRISPR/Cas9-mediated lethal counterselection in order to improve the efficiency with which recombinant S. aureus are recovered, which is especially useful in instances where mutants lack a selectable phenotype. These methods provide a rapid, scalable, precise, and inexpensive means to engineer point mutations, variable-length deletions, and short insertions into the S. aureus genome.
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Standard screening methods underreport AAV-mediated transduction and gene editing.
Conventional methods to discern adeno-associated virus (AAV) vector transduction patterns are based on high, stable expression of a reporter gene. As a consequence, conventionally described tropisms omit cell types that undergo transient transduction, or have low but undetectable levels of reporter expression. This creates a blind spot for AAV-based genome editing applications because only minimal transgene expression is required for activity. Here, we use editing-reporter mice to fill this void. Our approach sensitively captures both high and low transgene expression from AAV vectors. Using AAV8 and other serotypes, we demonstrate the superiority of the approach in a side-by-side comparison with traditional methods, demonstrate numerous, previously unknown sites of AAV targeting, and better predict the gene editing footprint after AAV-CRISPR delivery. We anticipate that this system, which captures the full spectrum of transduction patterns from AAV vectors in vivo, will be foundational to current and emerging AAV technologies.
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Optimized CRISPR/Cas9-mediated single nucleotide mutation in adherent cancer cell lines.
CRISPR/Cas9 is an efficient, accurate, and optimizable genome-editing tool. Here, we present a modified CRISPR/Cas9 genome-editing protocol for single nucleotide mutation in adherent cell lines. The protocol was adapted to focus on ease of use and efficiency. The protocol here describes how to generate a single nucleotide mutation in cultured 22Rv1 cells. We have also used the protocol in other adherent cell types. Thus, the protocol can be applied to assessing the effect of non-coding single nucleotide polymorphisms (SNPs) in a variety of cell types. For complete details on the use and execution of this protocol, please refer to Gao et al. (2018).
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TriCON: A Carbon-Based Triple-Modal Nanoplatform for Pancreatic Cancer Therapy.
Pancreatic cancer, recognized for its high malignancy and tumor immunosuppressive microenvironment, has been refractory to conventional therapeutic modalities, necessitating the exploration of novel treatment strategies. Among these, reprogramming of the tumor immunosuppressive microenvironment is a promising strategy to enhance the efficacy of tumor immunotherapy. The CRISPR/Cas9 system-based gene editing further offers a viable approach for precise regulation of endogenous gene expression associated with tumor immunosuppression. Current delivery vectors face a trilemma between biosafety profiles, expansion capacity, and targeting accuracy. To this end, we developed a triple-modality therapeutic platform, termed TriCON (Triple Convergent Oncology Nanotherapy), characterized by three core mechanistic attributes: spatiotemporal convergence, stimuli-responsive controllability, and tumor-microenvironment modulatory conductivity. This orchestrated combination of rationally designed gene editing (targeting poliovirus receptor), nano-encapsulated doxorubicin (DOX) chemotherapy, and checkpoint blockade immunotherapy demonstrated enhanced synergistic antitumor activity in pancreatic ductal adenocarcinoma (PDAC) models, achieving tumor regression through enhanced chemotherapy, immunogenic cell death induction, and natural killer (NK) cells activation. The platform achieved superior in vivo gene editing (14.2% PVR editing efficiency) via optimized endosomal escape and CRISPR system release. This triaxial approach establishes a programmable nanotherapeutic paradigm that synergizes gene editing precision with chemo-immunotherapy, offering a novel framework for PDAC treatment.
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