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Genetics experience impacts attitudes towards germline gene editing: a survey of over 1500 members of the public.
CRISPR-Cas9 has revolutionised genome engineering and has the potential to radically change our approach to genetic disease. However, the potential for genetic modification of embryos has raised significant and complex ethical and social concerns. The scientific community have called for ongoing stakeholder consultation about Germline Gene Editing (GGE), in particular lay publics, to help guide policy, education, research and regulatory priorities. In response, we conducted a survey to gauge public support for GGE and describe the demographic, experiential and contextual factors that influence individual attitudes. Respondent support was measured across nine hypothetical medical and enhancement GGE applications. We received responses from 1537 participants across 67 countries. Respondents were generally supportive of GGE, particularly for medical applications. While the most opposition observed was among religious respondents, those with work experience in genetics or genomics also reported greater resistance to GGE. Personal or family-related experience with genetics or genomics, identifying as female and tertiary education were also associated with less support for GGE. Further research needs to explore a diverse range of community and group attitudes towards GGE; the reasons underlying demographic and experiential differences; and to determine where the public and genetics professionals draw the line on ethical implementation respectively.
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A conversation with George Church.
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Potential of recombinant avian adeno-associated virus as a viral vector for CRISPR/Cas9 delivery to avian cells.
While genome editing has been established in chickens, where cultured primordial germ cell (PGC) systems are available, the implementation of genome editing remains a major challenge in many other birds due to the lack of robust PGC culture methods. Therefore, the development of reliable and efficient tools can significantly accelerate precision genome modification in avian species. Here, we evaluated the applicability of recombinant avian adeno-associated virus (rA3V) as a delivery vector for a CRISPR/Cas9 construct in avian cells using Staphylococcus aureus-derived Cas9 (SaCas9) and single-guide RNA (sgRNA). Infection with rA3V particles carrying an EGFP expression cassette (rA3V-EGFP) successfully induced EGFP expression in chicken fibroblasts (DF-1) cells, with approximately 80 % EGFP-positive cells at the maximum multiplicity of infection (MOI = 10,000). In plasmid-based transfection experiments, sgRNAs targeting the chicken tyrosinase locus and SaCas9 exhibited DNA cleavage activity in DF-1 cells. Furthermore, infection with rA3V particles encoding these CRISPR components successfully introduced indel mutations into the tyrosinase gene in DF-1 cells, with a calculated indel frequency of approximately 5.4 % at MOI = 40,000 without drug selection. Although EGFP expression was observed in quail fibrosarcoma cells, the percentage of EGFP-positive cells was much lower than that in DF-1 cells. In addition, in vivo infection with rA3V-EGFP of the chicken blastoderm failed to induce EGFP expression in germline cells, even at the highest applicable viral dose. In summary, rA3V can be used as a genome-editing vector in birds, although further investigation of its infectivity and tropism is necessary to expand its applicability to diverse avian species.
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Identification of a Novel Cleavage Site and Confirmation of the Effectiveness of NgAgo Gene Editing on RNA Targets.
Clusters of regularly interspaced short palindromic repeats (CRISPR)/Cas systems have a powerful ability to edit DNA and RNA targets. However, the need for a specific recognition site, protospacer adjacent motif (PAM), of the CRISPR/Cas system limits its application in gene editing. Some Argonaute (Ago) proteins have endonuclease functions under the guidance of 5' phosphorylated or hydroxylated guide DNA (gDNA). The NgAgo protein might perform RNA gene editing at 37 °C, suggesting its application in mammalian cells; however, its mechanisms are unclear. In the present study, the target of NgAgo in RNA was confirmed in vitro and in vivo. Then, an in vitro RNA cleavage system was designed and the cleavage site was verified by sequencing. Furthermore, NgAgo and gDNA were transfected into cells to cleave an intracellular target sequence. We demonstrated targeted degradation of GFP, HCV, and AKR1B10 RNAs in a gDNA-dependent manner by NgAgo both in vitro and in vivo, but no effect on DNA was observed. Sequencing demonstrated that the cleavage sites are located at the 3' of the target RNA which is recognized by 5' sequence of the gDNA. These results confirmed that NgAgo-gDNA cleaves RNA not DNA. We observed that the cleavage site is located at the 3' of the target RNA, which is a new finding that has not been reported in the past.
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Clinical perspective: Advancing hemophilia treatment through gene therapy approaches.
Hemophilia, a congenital bleeding disorder, can cause arthropathy, impaired mobility, pain, and life-threatening hemorrhage events, significantly impacting quality of life for patients and caregivers. Current therapies, although effective, necessitate costly lifelong treatment, often in specialized settings. However, as a monogenic disorder caused by loss-of-function genetic variants, hemophilia is amenable to gene therapy. In this article, three primary gene therapy approaches at the forefront of clinical development are reviewed. Adeno-associated virus-based gene therapy, having secured approval in the EU, UK, and US after promising phase 3 trial results, demonstrates clear superiority over standard-of-care treatment. Lentivirus-based approaches capable of transducing dividing and nondividing cells may improve the durability of treatment and have low susceptibility to pre-existing neutralizing antibodies to viral vectors. Finally, gene editing techniques such as zinc finger nucleases and CRISPR aim to correct genetic defects directly, holding promise as novel, effective, and highly durable therapeutic strategies in adults and children with hemophilia. This review provides a comprehensive summary of the current status of these gene therapy approaches, highlighting advantages, limitations, and potential future developments.
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Two is better than one: Advancing gene therapy protocols for enhanced safety and efficacy.
In this issue of Cell Stem Cell, two complementary studies from Zeng et al.1 and Demirci et al.2 improve the efficacy of gene therapy for β-hemoglobinopathies using multiplex CRISPR-Cas9 editing. The authors also optimize editing and conditioning protocols to reduce risks associated with current gene therapy procedures.
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Consolidating Ulva functional genomics: gene editing and new selection systems.
The green seaweed Ulva compressa is a promising model for functional biology. In addition to historical research on growth and development, -omics data and molecular tools for stable transformation are available. However, more efficient tools are needed to study gene function. Here, we expand the molecular toolkit for Ulva. We screened the survival of Ulva and its mutualistic bacteria on 14 selective agents and established that Blasticidin deaminases (BSD or bsr) can be used as selectable markers to generate stable transgenic lines. We show that Cas9 and Cas12a RNPs are suitable for targeted mutagenesis and can generate genomic deletions of up to 20 kb using the marker gene ADENINE PHOSPHORIBOSYLTRANSFERASE (APT). We demonstrate that the targeted insertion of a selectable marker via homology-directed repair or co-editing with APT is possible for nonmarker genes. We evaluated 31 vector configurations and found that the bicistronic fusion of Cas9 to a resistance marker or the incorporation of introns in Cas9 led to the most mutants. We used this to generate mutants in three nonmarker genes using a co-editing strategy. This expanded molecular toolkit now enables us to reliably make gain- and loss-of-function mutants; additional optimizations will be necessary to allow for vector-based multiplex genome editing in Ulva.
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Recruitment and rejoining of remote double-strand DNA breaks for enhanced and precise chromosome editing.
Chromosomal rearrangements, such as translocations, deletions, and inversions, underlie numerous genetic diseases and cancers, yet precise engineering of these rearrangements remains challenging. Here, we present a CRISPR-based homologous recombination-mediated rearrangement (HRMR) strategy that leverages homologous donor templates to align and repair broken chromosome ends. HRMR improves efficiency by approximately 80-fold compared to non-homologous end joining, achieving over 95% homologous recombination. Validated across multiple loci and cell lines, HRMR enables efficient and accurate chromosomal rearrangements. Live-cell imaging reveals that homologous donors mediate chromosome end proximity, enhancing rearrangement efficiency. Thus, HRMR provides a powerful tool for disease modeling, chromosomal biology, and therapeutic applications.
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Optimized paired-sgRNA/Cas9 cloning and expression cassette triggers high-efficiency multiplex genome editing in kiwifruit.
Kiwifruit is an important fruit crop; however, technologies for its functional genomic and molecular improvement are limited. The clustered regulatory interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system has been successfully applied to genetic improvement in many crops, but its editing capability is variable depending on the different combinations of the synthetic guide RNA (sgRNA) and Cas9 protein expression devices. Optimizing conditions for its use within a particular species is therefore needed to achieve highly efficient genome editing. In this study, we developed a new cloning strategy for generating paired-sgRNA/Cas9 vectors containing four sgRNAs targeting the kiwifruit phytoene desaturase gene (AcPDS). Comparing to the previous method of paired-sgRNA cloning, our strategy only requires the synthesis of two gRNA-containing primers which largely reduces the cost. We further compared efficiencies of paired-sgRNA/Cas9 vectors containing different sgRNA expression devices, including both the polycistronic tRNA-sgRNA cassette (PTG) and the traditional CRISPR expression cassette. We found the mutagenesis frequency of the PTG/Cas9 system was 10-fold higher than that of the CRISPR/Cas9 system, coinciding with the relative expressions of sgRNAs in two different expression cassettes. In particular, we identified large chromosomal fragment deletions induced by the paired-sgRNAs of the PTG/Cas9 system. Finally, as expected, we found both systems can successfully induce the albino phenotype of kiwifruit plantlets regenerated from the G418-resistance callus lines. We conclude that the PTG/Cas9 system is a more powerful system than the traditional CRISPR/Cas9 system for kiwifruit genome editing, which provides valuable clues for optimizing CRISPR/Cas9 editing system in other plants.
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Generation of genome-edited chicken and duck lines by adenovirus-mediated in vivo genome editing.
Conventional avian genome editing is mediated by isolation, culture, and genome editing of primordial germ cells (PGCs); screening and propagating the genome-edited PGCs; and transplantation of the PGCs into recipient embryos. The PGC-mediated procedures, however, are technically difficult, and therefore, the conventional method has previously been utilized only in chickens. Here, we generated germline mosaic founder chicken and duck lines without the PGC-mediated procedures by injecting an adenovirus containing the CRISPR-Cas9 system into avian blastoderms. Genome-edited chicken and duck offspring produced from the founders carried different insertion or deletion mutations without mutations in the potential off-target sites. Our data demonstrate successful applications of the adenovirus-mediated method for production of genome-edited chicken and duck lines.
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