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Gene Disruption Using Chemically Modified CRISPR-Cpf1 RNA.
CRISPR-based gene editing in mammalian cells is a powerful research tool which has demonstrated efficient site-specific gene modifications and is showing promise as a therapeutic for patients with genetic diseases. Multiple different CRISPR systems have been identified, each with its own target DNA recognition sequence, expanding the editable mammalian genome. It is also now appreciated that chemically modified nucleic acids can substitute for unmodified nucleotides in guide RNAs, providing protection from exonuclease degradation and improving gene editing efficiency. CRISPR-Cpf1 unlike CRISPR-Cas9, has a substantially lower propensity for off-target genomic cleavage, making it a preferred gene editing system for many applications. Here we provide a detailed protocol for use of CRISPR-Cpf1 and chemically modified guide RNAs in cell lines, outlining the steps from designing guide RNAs to a target gene of interest, delivery and expression in cells, and analysis of gene editing events.
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The Journey of Gene Therapy in Sickle Cell Disease: How Molecular Advances Meet Clinical Care.
Sickle cell disease (SCD) is a monogenic disorder responsible for recurrent vaso-occlusive crises, progressive organ damage, and shortened life expectancy. For decades, allogeneic hematopoietic stem cell transplantation from a matched sibling donor has been the only established cure, but its reach remains limited by donor availability and transplant-related toxicity. The approval of two autologous gene therapy products in 2023, exagamglogene autotemcel (exa-cel) and lovotibeglogene autotemcel (lovo-cel), marked a turning point for the SCD population and the gene therapy field in general. This review proposes a molecular rationale for fetal hemoglobin reactivation and β-globin gene addition, describes the engineering of lentiviral and CRISPR-based platforms, and highlights the clinical evidence accumulated to date that demonstrated durable disease modification with acceptable short-term toxicity. We then assess the clinical positioning of gene therapy within the broader spectrum of curative options compared to current available treatments and address the financial, ethical and psychosocial barriers that limit access to gene therapy both within high-income countries and globally. Critical research priorities include long-term safety surveillance, comparative effectiveness studies, pediatric trials below 12 years, and validated patient-reported outcome instruments. Base editing, non-genotoxic conditioning, and in vivo delivery represent the most promising avenues to broaden access and reduce treatment burden.
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Current progress in CRISPR-Cas systems for rare diseases.
The groundbreaking CRISPR-Cas gene editing method permits exact genetic code alteration. The "CRISPR" DNA protects bacteria from viruses. CRISPR-Cas utilizes a guide RNA to steer the Cas enzyme to the genome's gene editing target. After attaching to a sequence, Cas enzymes cleave DNA to insert, delete, or modify genes. The influence of CRISPR-Cas technology on molecular biology and genetics is profound. It allows for gene function research, animal disease models, and patient genetic therapy. Gene editing has transformed biotechnology, agriculture, and customized medicine. CRISPR-Cas could revolutionize genetics and medicine. CRISPR-Cas may accurately correct genetic flaws that underlie rare diseases, improving their therapy. Gene mutations make CRISPR-Cas gene editing a viable cure for uncommon diseases. We can use CRISPR-Cas to correct genetic abnormalities at the molecular level. This strategy offers hope for remedies and disease understanding. CRISPR-Cas genome editing may enable more targeted and effective treatments for rare medical illnesses with few therapy options. By developing base- and prime-editing CRISPR technology, CRISPR-Cas allows for accurate and efficient genome editing and advanced DNA modification. This advanced method provides precise DNA alterations without double-strand breakage. These advances have improved gene editing safety and precision, reducing unfavorable effects. Lipid nanoparticles, which use viral vectors, improve therapeutic cell and tissue targeting. In rare disorders, gene therapy may be possible with CRISPR-Cas clinical trials. CRISPR-Cas research is improving gene editing, delivery, and rare disease treatment.
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CRISPR-free RNA base editing mediated PTC-readthrough restores hearing in mice with Otof nonsense mutation.
The gene therapy achieved by AAV-mediated otoferlin-overexpression is an effective therapeutic strategy for congenital deafness. However, achieving its physiological and endogenous patterns of expression remains challenging. Here, we generate the homologous mutation Otof c.1315 C > T (p.R439*), equivalent to OTOF c.1273 C > T (p.R425*) found in humans with profound deafness, to create a nonsense mutation-induced deaf mouse model. We then deliver the 'RESTART v3' system, which is a CRISPR-free RNA base editor for nonsense mutation suppression, into the cochlea of the mice. We achieve physiological otoferlin expression, and the edited premature termination codon is reverse-mutated to the original amino acid. We observe significant hearing restoration and enhancement of the behavioral auditory startle reflex. Thus, our study presents a successful RNA editing strategy to significantly restore hereditary deafness in mice carrying the specific Otof nonsense mutation, which holds great promise for future clinical translation.
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Gene Editing by Ferrying of CRISPR/Cas Ribonucleoprotein Complexes in Enveloped Virus-Derived Particles.
The invention of next-generation CRISPR/Cas gene editing tools, like base and prime editing, for correction of gene variants causing disease, has created hope for in vivo use in patients leading to wider clinical translation. To realize this potential, delivery vehicles that can ferry gene editing tool kits safely and effectively into specific cell populations or tissues are in great demand. In this review, we describe the development of enveloped retrovirus-derived particles as carriers of "ready-to-work" ribonucleoprotein complexes consisting of Cas9-derived editor proteins and single guide RNAs. We present arguments for adapting viruses for cell-targeted protein delivery and describe the status after a decade-long development period, which has already shown effective editing in primary cells, including T cells and hematopoietic stem cells, and in tissues targeted in vivo, including mouse retina, liver, and brain. Emerging evidence has demonstrated that engineered virus-derived nanoparticles can accommodate both base and prime editors and seems to fertilize a sprouting hope that such particles can be further developed and produced in large scale for therapeutic applications.
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Modulating Cas9 activity for precision gene editing.
The CRISPR/Cas9 is a RNA-guided nuclease complex that can be specifically programmed to target a user-specified DNA sequence. It has been a powerful and effective tool of genome editing. However, off-target activity of the Cas9 nuclease limits its potential use in the correction of inherited diseases and bona fide gene editing. Various protein engineering and guide RNA selection strategies have been utilized to improve Cas9-based genome-editing specificity and efficiency. We, however, have not yet achieved a degree of safety such that Cas9 gene editing approaches could be applicable in clinical settings. Here, we discuss the recently developed and precise gene editing technologies based on spCas9. Furthermore, we describe Cas9 modulating tools to increase the fidelity of the CRISPR/Cas9 system. These studies suggest that there is still a need for pharmaceutical modulation of Cas9 activity during gene editing procedures. Pharmaceutical modulation of Cas9 nuclease activity at on-target or off-target genomic loci could 1 day allow researchers to develop robust and precise therapeutical strategies in gene editing.
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Perfecting Targeting in CRISPR.
CRISPR-based genome editing holds promise for genome engineering and other applications in diverse organisms. Defining and improving the genome-wide and transcriptome-wide specificities of these editing tools are essential for realizing their full potential in basic research and biomedical therapeutics. This review provides an overview of CRISPR-based DNA- and RNA-editing technologies, methods to quantify their specificities, and key solutions to reduce off-target effects for research and improve therapeutic applications.
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CRISPR-free base editors with enhanced activity and expanded targeting scope in mitochondrial and nuclear DNA.
The all-protein cytosine base editor DdCBE uses TALE proteins and a double-stranded DNA-specific cytidine deaminase (DddA) to mediate targeted C•G-to-T•A editing. To improve editing efficiency and overcome the strict TC sequence-context constraint of DddA, we used phage-assisted non-continuous and continuous evolution to evolve DddA variants with improved activity and expanded targeting scope. Compared to canonical DdCBEs, base editors with evolved DddA6 improved mitochondrial DNA (mtDNA) editing efficiencies at TC by 3.3-fold on average. DdCBEs containing evolved DddA11 offered a broadened HC (H = A, C or T) sequence compatibility for both mitochondrial and nuclear base editing, increasing average editing efficiencies at AC and CC targets from less than 10% for canonical DdCBE to 15-30% and up to 50% in cell populations sorted to express both halves of DdCBE. We used these evolved DdCBEs to efficiently install disease-associated mtDNA mutations in human cells at non-TC target sites. DddA6 and DddA11 substantially increase the effectiveness and applicability of all-protein base editing.
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New advances in CRISPR/Cas-mediated precise gene-editing techniques.
Over the past decade, CRISPR/Cas-based gene editing has become a powerful tool for generating mutations in a variety of model organisms, from Escherichia coli to zebrafish, rodents and large mammals. CRISPR/Cas-based gene editing effectively generates insertions or deletions (indels), which allow for rapid gene disruption. However, a large proportion of human genetic diseases are caused by single-base-pair substitutions, which result in more subtle alterations to protein function, and which require more complex and precise editing to recreate in model systems. Precise genome editing (PGE) methods, however, typically have efficiencies of less than a tenth of those that generate less-specific indels, and so there has been a great deal of effort to improve PGE efficiency. Such optimisations include optimal guide RNA and mutation-bearing donor DNA template design, modulation of DNA repair pathways that underpin how edits result from Cas-induced cuts, and the development of Cas9 fusion proteins that introduce edits via alternative mechanisms. In this Review, we provide an overview of the recent progress in optimising PGE methods and their potential for generating models of human genetic disease.
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Scalable purification enables high-quality virus-like particles for therapeutic translation.
Emerging molecular therapies introduce enzymatic activity into cells by delivering genes, transcripts, or proteins. Owing to their robust cell-entry capacity, virus-like particles (VLPs) represent a technology of choice in genome editing, where low doses of heterologous proteins and nucleic acids are essential. However, clinical translation of VLP vectors is hindered by inadequate purification methods. Current approaches, relying primarily on ultracentrifugation, suffer from inconsistent product quality and poor scalability. Here, we report the development of a broadly applicable purification strategy that improves the purity and therapeutic efficacy of genome-editing VLPs. Considering the characteristic properties of murine leukemia virus-derived engineered VLPs and HIV-derived engineered nucleocytosolic vehicles for loading of programmable editors, we developed a workflow that involves single-modal and multimodal chromatographic steps, effectively removing host cell proteins and cell-culture contaminants while improving VLP integrity and biological activity. Our purified VLPs displayed superior protein composition, consistency, and enhanced functional delivery compared to VLPs partially purified by conventional ultracentrifugation methods. Mass spectrometric analysis revealed a substantial decrease in contaminants, with VLP-specific proteins comprising >90% of the final product. In vivo studies confirmed improved therapeutic outcomes when chromatographically purified VLPs were used. Our scalable purification platform addresses critical manufacturing bottlenecks and constitutes a starting point for further development of VLP therapeutics, enabling robust production of pure VLPs for diverse applications such as genome editing, vaccine development, and other uses that require intracellular protein delivery.
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