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Broadening the Nicotiana benthamiana research toolbox through the generation of dicer-like mutants using CRISPR/Cas9 approaches.
RNA silencing in plants plays a pivotal role in various biological processes, including development, epigenetic modifications and stress response. Key components of this network are Dicer-like (DCL) proteins. Nicotiana benthamiana encodes four DCLs, each responsible for the generation of distinct small RNA (sRNA) populations, which regulate different functions. However, elucidating the precise role of each DCL has been proven challenging, as overlapping functions exist within DCLs. In our present study, we have successfully generated dcl2, dcl3 and dcl4 homozygous mutants, employing two different CRISPR/Cas9 approaches. The first approach is based on a transgene-mediated delivery of the single-guide RNA (sgRNA), while the second approach employs a viral vector for sgRNA delivery. By utilizing a suite of screening techniques, including polymerase chain reaction (PCR), T7 endonuclease I (T7E1) assay, high-resolution melt analysis (HRMA) and DNA sequencing, we successfully generated dcl2, dcl3 and dcl4 homozygous mutants harboring identical mutations in every allele. To evaluate these dcl mutants, we examined their sRNA profiles and phenotypes. We further have indications that homozygous mutations of a gene do not always lead to the desired loss-of-function, highlighting the importance of mutant evaluation. dcl mutants represent invaluable tools to explore how overlapping silencing pathways are connected to essential plant functions, including development, stress responses and pathogen defense. Additionally, they hold potential for biotechnological applications, such as crop improvement and gene silencing tools. We anticipate that our study will make significant contributions to enhance understanding of the role of DCLs in plants.
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Current Challenges With Highly Active Antiretroviral Therapy and New Hope and Horizon With CRISPR-CAS9 Technology for HIV Treatment.
Clustered regularly interspaced short palindromic repeats (CRISPR/Cas system) is now the predominant approach for genome editing. Compared to conventional genetic editing methods, CRISPR/Cas technology offers several advantages that were previously unavailable. Key benefits include the ability to simultaneously modify multiple locations, reduced costs, enhanced efficiency, and a more user-friendly design. By directing Cas-mediated DNA cleavage to specific genomic targets and utilizing intrinsic DNA repair processes, this system can produce site-specific gene modifications. This goal is achieved through an RNA-guided procedure. As the most effective gene editing method currently available, the CRISPR/Cas system has proven to be highly valuable in genomic research across a wide range of species since its discovery as a component of the adaptive immune system in bacteria. Its applicability extends to various organisms, making it increasingly prevalent in the medical field, where it shows great promise in investigating viral infections, cancer, and genetic disorders. Furthermore, it enhances our understanding of fundamental genetics. This article outlines the current antiretroviral therapy and its adverse effects but also CRISPR/Cas technology. This review article also discusses its mechanism of action and potential applications in the treatment of HIV/AIDS.
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Impact of CRISPR interference on strain development in biotechnology.
Genetic perturbation systems are of great interest to redirect metabolic fluxes for value-added production, as well as genetic screening for the development of new drugs, or to identify new targets for biotechnological applications. Here, we review CRISPR interference (CRISPRi), a method for gene expression using a catalytically inactive version of the CRISPR-associated protein 9 (dCas9) of the widely applied CRISPR-Cas9 genome editing system. In combination with the appropriate sgRNA, dCas9 binds to specific DNA sequences without causing double-stranded DNA breakage but interfering with transcription initiation or elongation. Besides manifold uses to interrogate the physiology of a bacterial cell, CRISPRi is used in applications for metabolic engineering and strain development in industrial biotechnology. Albeit in its infancy, CRISPRi has already delivered the first success stories; however, we also analyze limitations of the CRISPRi system and give future perspectives.
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In vivo genome editing improves muscle function in a mouse model of Duchenne muscular dystrophy.
Duchenne muscular dystrophy (DMD) is a devastating disease affecting about 1 out of 5000 male births and caused by mutations in the dystrophin gene. Genome editing has the potential to restore expression of a modified dystrophin gene from the native locus to modulate disease progression. In this study, adeno-associated virus was used to deliver the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system to the mdx mouse model of DMD to remove the mutated exon 23 from the dystrophin gene. This includes local and systemic delivery to adult mice and systemic delivery to neonatal mice. Exon 23 deletion by CRISPR-Cas9 resulted in expression of the modified dystrophin gene, partial recovery of functional dystrophin protein in skeletal myofibers and cardiac muscle, improvement of muscle biochemistry, and significant enhancement of muscle force. This work establishes CRISPR-Cas9-based genome editing as a potential therapy to treat DMD.
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CRISPR-Cas system in microbial hosts for terpenoid production.
Terpenoids represent the largest group of secondary metabolites with variable structures and functions. Terpenoids are well known for their beneficial application in human life, such as pharmaceutical products, vitamins, hormones, anticancer drugs, cosmetics, flavors and fragrances, foods, agriculture, and biofuels. Recently, engineering microbial cells have been provided with a sustainable approach to produce terpenoids with high yields. Noticeably, the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system has emerged as one of the most efficient genome-editing technologies to engineer microorganisms for improving terpenoid production. In this review, we summarize the application of the CRISPR-Cas system for the production of terpenoids in microbial hosts such as Escherichia coli, Saccharomyces cerevisiae, Corynebacterium glutamicum, and Pseudomonas putida. CRISPR-Cas9 deactivated Cas9 (dCas9)-based CRISPR (CRISPRi), and the dCas9-based activator (CRISPRa) have been used in either individual or combinatorial systems to control the metabolic flux for enhancing the production of terpenoids. Finally, the prospects of using the CRISPR-Cas system in terpenoid production are also discussed.
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CRISPR/Cas-mediated genome editing in mice for the development of drug delivery mechanism.
BACKGROUND: To manipulate particular locations in the bacterial genome, researchers have recently resorted to a group of unique sequences in bacterial genomes that are responsible for safeguarding bacteria against bacteriophages. Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) are two such systems, each of which consists of an RNA component and an enzyme component. METHODS AND RESULTS: This review focuses primarily on how CRISPR/Cas9 technology can be used to make models to study human diseases in mice. Creating RNA molecules that direct endonucleases to a specific position in the genome are crucial for achieving a specific genetic modification. CRISPR/Cas9 technology has allowed scientists to edit the genome with greater precision than ever before. Researchers can use knock-in and knock-out methods to model human diseases such as Neurological, cardiovascular disease, and cancer. CONCLUSIONS: In terms of developing innovative methods to discover ailments for diseases/disorders, improved CRISPR/Cas9 technology will provide easier access to valuable novel animal models.
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An in-library ligation strategy and its application in CRISPR/Cas9 screening of high-order gRNA combinations.
Simultaneous targeting multiple genes is a big advantage of CRISPR (clustered regularly interspaced short palindromic repeats) genome editing but challenging to achieve in CRISPR screening. The crosstalk among genes or gene products is a common and fundamental mechanism to ensure cellular stability and functional diversity. However, the screening approach to map high-order gene combinations to the interesting phenotype is still lacking. Here, we developed a universal in-library ligation strategy and applied it to generate multiplexed CRISPR library, which could perturb four pre-designed targets in a cell. We conducted in vivo CRISPR screening for potential guide RNA (gRNA) combinations inducing anti-tumor immune responses. Simultaneously disturbing a combination of three checkpoints in CD8+ T cells was demonstrated to be more effective than disturbing Pdcd1 only for T cell activation in the tumor environment. This study developed a novel in-library ligation strategy to facilitate the multiplexed CRISPR screening, which could extend our ability to explore the combinatorial outcomes from coordinated gene behaviors.
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Dual-Locking Nanoparticles Disrupt the PD-1/PD-L1 Pathway for Efficient Cancer Immunotherapy.
The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) enzyme, Cas13a, holds great promise in cancer treatment due to its potential for selective destruction of tumor cells via collateral effects after target recognition. However, these collateral effects do not specifically target tumor cells and may cause safety issues when administered systemically. Herein, a dual-locking nanoparticle (DLNP) that can restrict CRISPR/Cas13a activation to tumor tissues is described. DLNP has a core-shell structure, in which the CRISPR/Cas13a system (plasmid DNA, pDNA) is encapsulated inside the core with a dual-responsive polymer layer. This polymer layer endows the DLNP with enhanced stability during blood circulation or in normal tissues and facilitates cellular internalization of the CRISPR/Cas13a system and activation of gene editing upon entry into tumor tissue. After carefully screening and optimizing the CRISPR RNA (crRNA) sequence that targets programmed death-ligand 1 (PD-L1), DLNP demonstrates the effective activation of T-cell-mediated antitumor immunity and the reshaping of immunosuppressive tumor microenvironment (TME) in B16F10-bearing mice, resulting in significantly enhanced antitumor effect and improved survival rate. Further development by replacing the specific crRNA of target genes can potentially make DLNP a universal platform for the rapid development of safe and efficient cancer immunotherapies.
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Gene Editing in Chronic Granulomatous Disease.
Chronic granulomatous disease (CGD) is an immune deficiency characterized by defects in the production of microbicidal reactive oxygen species (ROS) by the phagocytic oxidase (phox) enzyme complex in neutrophils. We have previously described targeted gene editing strategies using zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), or clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 nucleases for gene targeting with homology-directed repair in CGD patient stem cells to achieve functional restoration of expression of phox genes and NADPH oxidase activity in differentiated neutrophils. In this chapter, we describe detailed protocols for targeted gene editing in human-induced pluripotent stem cells and hematopoietic stem cells and for subsequent differentiation of these stem cells into mature neutrophils, as well as assays to characterize neutrophil identity and function including flow cytometry analysis of neutrophil surface markers, intracellular staining for phox proteins, and analysis of ROS generation.
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Immunogenicity of Cas9 Protein.
Clustered regularly interspaced short palindromic repeats (CRISPR) form the adaptive immune system in archaea and bacteria and have been modified for genome engineering in eukaryotic cells. CRISPR systems contain 2 components, a single-guide RNA, which is a short RNA composed of a 20 nucleotide sequence that targets specific sites in the genomic DNA and a scaffold necessary for its binding to the CRISPR-associated endonuclease (Cas9). Because of its high efficiency and accuracy, the CRISPR-Cas9 genome editing based therapies are poised to treat a multitude of human diseases with a promise to target previously "undruggable" proteins. As the first in-body clinical trial with CRISPR-Cas9 is embarked on, the risks associated with administering the genome editing machinery to patients become increasingly relevant. Recent studies have demonstrated an innate and adaptive cellular immune response to Cas9 in mouse models and the presence of anti-Cas9 antibodies and T-cells in human plasma. Pre-existing immunity against therapeutic Cas9 delivery could decrease its efficacy in vivo and may pose significant safety issues. This review focuses on the immunogenicity of the Cas9 protein and summarizes potential approaches to circumvent the problem of immune recognition.
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