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More abundant and healthier meat: will the MSTN editing epitome empower the commercialization of gene editing in livestock?
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CRISPR/Cas9-Mediated Genome Editing in Comfrey (Symphytum officinale) Hairy Roots Results in the Complete Eradication of Pyrrolizidine Alkaloids.
Comfrey (Symphytum officinale) is a medicinal plant with anti-inflammatory, analgesic, and proliferative properties. However, its pharmaceutical application is hampered by the co-occurrence of toxic pyrrolizidine alkaloids (PAs) in its tissues. Using a CRISPR/Cas9-based approach, we introduced detrimental mutations into the hss gene encoding homospermidine synthase (HSS), the first pathway-specific enzyme of PA biosynthesis. The resulting hairy root (HR) lines were analyzed for the type of gene-editing effect that they exhibited and for their homospermidine and PA content. Inactivation of only one of the two hss alleles resulted in HRs with significantly reduced levels of homospermidine and PAs, whereas no alkaloids were detectable in HRs with two inactivated hss alleles. PAs were detectable once again after the HSS-deficient HRs were fed homospermidine confirming that the inability of these roots to produce PAs was only attributable to the inactivated HSS and not to any unidentified off-target effect of the CRISPR/Cas9 approach. Further analyses showed that PA-free HRs possessed, at least in traces, detectable amounts of homospermidine, and that the PA patterns of manipulated HRs were different from those of control lines. These observations are discussed with regard to the potential use of such a CRISPR/Cas9-mediated approach for the economical exploitation of in vitro systems in a medicinal plant and for further studies of PA biosynthesis in non-model plants.
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Unleashing the potential: type I CRISPR-Cas systems in actinomycetes for genome editing.
Covering: up to the end of 2023Type I CRISPR-Cas systems are widely distributed, found in over 40% of bacteria and 80% of archaea. Among genome-sequenced actinomycetes (particularly Streptomyces spp.), 45.54% possess type I CRISPR-Cas systems. In comparison to widely used CRISPR systems like Cas9 or Cas12a, these endogenous CRISPR-Cas systems have significant advantages, including better compatibility, wide distribution, and ease of operation (since no exogenous Cas gene delivery is needed). Furthermore, type I CRISPR-Cas systems can simultaneously edit and regulate genes by adjusting the crRNA spacer length. Meanwhile, most actinomycetes are recalcitrant to genetic manipulation, hindering the discovery and engineering of natural products (NPs). The endogenous type I CRISPR-Cas systems in actinomycetes may offer a promising alternative to overcome these barriers. This review summarizes the challenges and recent advances in CRISPR-based genome engineering technologies for actinomycetes. It also presents and discusses how to establish and develop genome editing tools based on type I CRISPR-Cas systems in actinomycetes, with the aim of their future application in gene editing and the discovery of NPs in actinomycetes.
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Improving soybean fatty acid profiles by CRISPR/Cas12a-mediated gene editing of GmFAD2 and GmFAD3.
Using CRISPR/Cas12a, we engineered novel soybean germplasms by knocking out GmFAD2 (GmFAD2-1A, GmFAD2-1B) and GmFAD3 (GmFAD3A, GmFAD3B) genes, yielding elevated oleic or linoleic acid content. Soybean oil contains high levels of polyunsaturated fatty acids (PUFAs), which are known to reduce cholesterol levels and help prevent hypertension, thereby contributing significantly to human health. However, the chemical instability of PUFAs makes them susceptible to oxidation, a process that generates harmful trans-fatty acids. To address this issue, precise modulation of fatty acid composition in soybeans becomes critically important for health applications. In this study, we employed CRISPR/Cas12a gene editing technology to selectively knock out the GmFAD2 (GmFAD2-1A, GmFAD2-1B) and GmFAD3 (GmFAD3A, GmFAD3B) genes in soybean. This approach successfully created novel soybean germplasms with distinct fatty acid profiles: one with elevated oleic acid content and another with increased linoleic acid levels. These engineered variants provide valuable options for utilizing soybean oil with optimized fatty acid compositions tailored for specific health and nutritional purposes.
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A CRISPR-Cas9 system for knock-out and knock-in of high molecular weight DNA enables module-swapping of the pikromycin synthase in its native host.
BACKGROUND: Engineers seeking to generate natural product analogs through altering modular polyketide synthases (PKSs) face significant challenges when genomically editing large stretches of DNA. RESULTS: We describe a CRISPR-Cas9 system that was employed to reprogram the PKS in Streptomyces venezuelae ATCC 15439 that helps biosynthesize the macrolide antibiotic pikromycin. We first demonstrate its precise editing ability by generating strains that lack megasynthase genes pikAI-pikAIV or the entire pikromycin biosynthetic gene cluster but produce pikromycin upon complementation. We then employ it to replace 4.4-kb modules in the pikromycin synthase with those of other synthases to yield two new macrolide antibiotics with activities similar to pikromycin. CONCLUSION: Our gene-editing tool has enabled the efficient replacement of extensive and repetitive DNA regions within streptomycetes.
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Assessing gene function in human B cells: CRISPR/Cas9-based gene editing and mRNA-based gene expression in healthy and tumor cells.
Robust methods for manipulation of human B cells, isolated from healthy donors and patients with B cell disorders, has the potential to significantly accelerate B cell research. Our work describes a step-by-step protocol to perform electroporation-based screening of gene function in B cells through the use of Cas9 ribonuclecomplexes and in vitro produced mRNA.
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CRISPR/Cas9: a breakthrough in generating mouse models for endocrinologists.
CRISPR/Cas9 is a recent development in genome editing which is becoming an indispensable element of the genetic toolbox in mice. It provides outstanding possibilities for targeted modification of the genome, and is often extremely efficient. There are currently two main limitations to in ovo genome editing in mice: the first is mosaicism, which is frequent in founder mice. The second is the difficulty to evaluate the advent of off-target mutations, which often imposes to wait for germline transmission to ensure genetic segregation between wanted and unwanted genetic mutations. However rapid progresses are made, suggesting that these difficulties can be overcome in the near future.
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Rational Design of ssODN to Correct Mutations by Gene Editing.
Gene editing allows to make a variety of targeted changes in genome, which can potentially be used to treat hereditary human diseases. Despite numerous studies in this area, effectiveness of gene editing methods for correcting mutations is still low, so these methods are not allowed in routine practice. It has been shown that rational design of genome editing components can significantly increase efficiency of mutation correction. In this work, we propose design of single-stranded oligodeoxyribonucleotides (ssODNs) to increase efficiency of gene editing. Using a model system to repair knocked out EGFP that is integrated into the genome of HEK293T cell culture, we have shown that only a small part of ssODN (about 20 nucleotides: from the 15th nucleotide at 3'-end to the 4th nucleotide at 5'-end), a donor molecule for repairing double-stranded DNA breaks, is integrated into the site of the break. Based on the obtained data, it is possible to rationally approach the design of ssODNs to correct mutations using CRISPR-Cas9 method for the development of gene therapy for hereditary human diseases.
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Transgene-Free, Gene-Edited Cavendish Bananas (Musa acuminata, AAA).
Global consumer acceptance of gene-edited food crops is increasing with new breeding technologies that can modify the genome without foreign DNA integration. Here, we report an Agrobacterium-based system for transgene-free, gene editing of the banana cultivar, Cavendish. The protocol uses a three-tiered approach whereby cells containing T-DNA are enriched by positive antibiotic selection over a 48-h period, CRISPR/Cas9-mediated gene editing occurs over a short transient window and negative selection of cells containing T-DNA is achieved by the addition of 5-FC, which is converted to cytotoxic 5-FU by the co-expressed CODA enzyme. Two key enzymes in the carotenoid biosynthesis pathway were targeted as visual markers of editing: phytoene desaturase (pds) and lycopene β-cyclase (LCYb). Disruptive edits of the LCYb gene were easily identifiable at the calli stage of the regeneration process with cells appearing pink due to lycopene accumulation. Eight of 32 plants for pds and 34 of 125 plants for LCYb contained edits and were likely free of integrated vector DNA as determined by targeted genome sequencing and T-DNA-specific PCR, respectively. Plants containing disruptive tri-allelic edits in either gene displayed an albino phenotype. A subset of potentially transgene-free, edited plants was verified by whole genome sequencing. The transient editing protocol has an estimated 17.6% to 21.9% efficiency in generating plants containing disruptive tri-allelic modifications that are free of novel DNA. The protocol overcomes the regulatory limitations associated with the release of gene-edited, vegetatively propagated crops and provides an effective means of creating new disease-resistant and agronomically superior Cavendish cultivars.
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Emerging applications of gene edited T cells for the treatment of leukemia.
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