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Creation of zebrafish knock-in reporter lines in the nefma gene by Cas9-mediated homologous recombination.
CRISPR/Cas9-based strategies are widely used for genome editing in many organisms, including zebrafish. Although most applications consist in introducing double strand break (DSB)-induced mutations, it is also possible to use CRISPR/Cas9 to enhance homology directed repair (HDR) at a chosen genomic location to create knock-ins with optimally controlled precision. Here, we describe the use of CRISPR/Cas9-targeted DSB followed by HDR to generate zebrafish transgenic lines where exogenous coding sequences are added in the nefma gene, in frame with the endogenous coding sequence. The resulting knock-in embryos express the added gene (fluorescent reporter or KalTA4 transactivator) specifically in the populations of neurons that express nefma, making them convenient tools for research on these populations.
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Strategies for generation of mice via CRISPR/HDR-mediated knock-in.
CRISPR/Cas9 framework is generally used to generate genetically modified mouse models. The clustered regularly interspaced short palindromic repeat gene editing technique, can efficiently generate knock-outs using the non-homologous end-joining repair pathway. Small knock-ins also work precisely using a repair template with help of homology-directed-repair (HDR) mechanism. However, when the fragment size is larger than 4-5 kb, the knock-in tends to be error prone and the efficiency decreases. Certain types of modifications, in particular insertions of very large DNA fragments (10-100 kb) or entire gene replacements, are still difficult. The HDR process needs further streamlining and improvement. Here in this review, we describe methods to enhance the efficiency of the knock-in through checking each step from the guide design to the microinjection and choice of the oocyte donors. This helps in understanding the parameters that can be modified to get improved knock-in efficiency via CRISPR targeting.
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Development of a RecE/T-Assisted CRISPR-Cas9 Toolbox for Lactobacillus.
Lactobacilli are members of a large family involved in industrial food fermentation, therapeutics, and health promotion. However, the development of genetic manipulation tools for this genus lags behind its relative industrial and medical significance. The development of clustered regularly interspaced short palindromic repeat (CRISPR)-based genome engineering for Lactobacillus is now underway. However, some Lactobacillus species are sensitive to CRISPR-Cas9 induced double strand breaks (DSBs) due to a deficiency in homology-directed repair (HDR), which allows chromosomal genetic editing. Here, phage-derived RecE/T is coupled with CRISPR-Cas9 and the transcriptional activity of broad-spectrum host promoters is assessed to set up a versatile toolbox containing a recombination helper plasmid and a broad host CRISPR-Cas9 editing plasmid, which enables efficient genome editing in Lactobacillus plantarum (L. plantarum) WCFS1 and Lactobacillus brevis (L. brevis) ATCC367. The RecE/T-assisted CRISPR-Cas9 toolbox realizes single gene deletions at an efficiency of 50-100% in seven days. Furthermore, the chromosomal gene replacement of Lp_0537 using a P23 -pyruvate decarboxylase (pdc) expression cassette is accomplished with an efficiency of 35.7%. This study establises a RecE/T-assisted CRISPR genome editing toolbox for L. plantarum WCFS1 and L. brevis ATCC367 and also demonstrate that RecE/T-assisted CRISPR-Cas9 is an effective genome editing system, which can be readily implemented in Lactobacilli.
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Development of Resistance to Damping-Off in Rice, Oryza sativa L., Using CRISPR/Cas9.
Damping-off disease hinders rice seedling growth and reduces yield. Current control methods, such as seed or soil sterilization, rely on chemicals that cause environmental pollution and promote pathogen resistance. As a sustainable alternative, we targeted the damping-off resistance-related gene OsDGTq1 using CRISPR/Cas9. Field experiments first verified OsDGTq1's significance in resistance. The CRISPR/Cas9 system, delivered via Agrobacterium-mediated transformation, was used to edit OsDGTq1 in rice cultivar Ilmi. Lesions from major damping-off pathogens, Rhizoctonia solani and Pythium graminicola, were observed on G0 plants. All 37 regenerated plants contained T-DNA insertions. Among them, edits generated by sgRNA1-1, sgRNA1-2, and sgRNA1-3 resulted in the insertion of two thymine bases as target mutations. Edited lines were assigned names and evaluated for agronomic traits, seed-setting rates, and pathogen responses. Several lines with edited target genes showed distinct disease responses and altered gene expression compared to Ilmi, likely due to CRISPR/Cas9-induced sequence changes. Further studies in subsequent generations are needed to confirm the stability of these edits and their association with resistance. These results confirm that genome editing of OsDGTq1 alters resistance to damping-off. The approach demonstrates that gene-editing technology can accelerate rice breeding, offering an environmentally friendly strategy to develop resistant varieties. Such varieties can reduce chemical inputs, prevent pollution, and minimize seedling loss, ultimately enhancing food self-sufficiency and stabilizing rice supply.
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Lipofection with Lipofectamine™ 2000 in a heparin-free growth medium results in high transfection efficiency in chicken primordial germ cells.
Primordial germ cells (PGCs) that can differentiate into gametes are used to produce genome-edited chickens. However, the transfection efficiency into PGCs is low in chickens; therefore, the yield efficiency of PGCs modified via genome editing is problematic. In this study, we improved transfection efficiency and achieved highly efficient genome editing in chicken PGCs. For transfection, we used lipofection, which is convenient for gene transfer. Chicken PGC cultures require adding heparin to support growth; however, heparin significantly reduces lipofection efficiency (p < 0.01). Heparin-induced lipofection efficiency was restored by adding protamine. Based on these results, we optimized gene transfer into chicken PGCs. Lipofectamine 2000 and our PGC medium were the most efficient transfection reagent and medium, respectively. Finally, based on established conditions, we compared the gene knock-out efficiencies of ovomucoid, a major egg allergen, and gene knock-in efficiencies at the ACTB locus. These results indicate that optimized lipofection is useful for CRISPR/Cas9-mediated knock-out and knock-in. Our findings may contribute to the generation of genome-edited chickens and stimulate research in various applications involving them.
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Simplification of nutritional conditions in transformation procedures for genome editing with the CRISPR/Cas9 system for fission yeast.
CRISPR/Cas9 is a powerful tool for genome editing. Several studies have been conducted to take the benefit of the versatile tool in the fission yeast Schizosaccharomyces pombe. However, the protocols for the CRISPR/Cas9 system proposed in previous studies are complicated in culture conditions compared to traditional genome editing methods. In this study, we introduced vectors for expression of sgRNA as well as Cas9, which employ natMX6 and bsdMX6 dominant selection markers. Using these materials, we examined nutritional conditions of cell cultures and found that nitrogen depletion introduced in previous methods does not affect the efficiency of genome editing. We found that bsdMX6-based plasmids enable us to skip any recovery steps before plating onto medium containing blasticidin S, unlike other antibiotic resistance selection markers. We thus propose easier transformation procedures with natMX6 and particularly bsdMX6 markers. We also simulate prescreening of mutants by genotyping with DNA endonucleases or proofreading PCR instead of relying on existing knowledge of mutant phenotypes. These materials and methods assist easy construction of S. pombe strains using CRISPR/Cas9, thereby accelerating seamless introduction of CRISPR/Cas9 to S. pombe researchers.
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Highly efficient DNA-free plant genome editing using virally delivered CRISPR-Cas9.
Genome-editing technologies using CRISPR-Cas nucleases have revolutionized plant science and hold enormous promise in crop improvement. Conventional transgene-mediated CRISPR-Cas reagent delivery methods may be associated with unanticipated genome changes or damage1,2, with prolonged breeding cycles involving foreign DNA segregation and with regulatory restrictions regarding transgenesis3. Therefore, DNA-free delivery has been developed by transfecting preassembled CRISPR-Cas9 ribonucleoproteins into protoplasts4 or in vitro fertilized zygotes5. However, technical difficulties in regeneration from these wall-less cells make impractical a general adaption of these approaches to most crop species. Alternatively, CRISPR-Cas ribonucleoproteins or RNA transcripts have been biolistically bombarded into immature embryo cells or calli to yield highly specific genome editing, albeit at low frequency6-9. Here we report the engineering of a plant negative-strand RNA virus-based vector for DNA-free in planta delivery of the entire CRISPR-Cas9 cassette to achieve single, multiplex mutagenesis and chromosome deletions at high frequency in a model allotetraploid tobacco host. Over 90% of plants regenerated from virus-infected tissues without selection contained targeted mutations, among which up to 57% carried tetra-allelic, inheritable mutations. The viral vector remained stable even after mechanical transmission, and can readily be eliminated from mutated plants during regeneration or after seed setting. Despite high on-target activities, off-target effects, if any, are minimal. Our study provides a convenient, highly efficient and cost-effective approach for CRISPR-Cas9 gene editing in plants through virus infection.
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The Advancement of Prime Editing Technology.
The advent of CRISPR/Cas genome editing has spurred major breakthroughs across life sciences, offering vast potential across numerous research and application fields. Among the expanding toolkit of CRISPR/Cas-derived methods, prime editing (PE) stands out for its versatility and specificity, enabling precise point mutations and small insertions or deletions without requiring double-stranded DNA breaks. Since its introduction, PE has undergone multiple rounds of optimization to improve performance. In this review, the core components and mechanism of prime editors, followed by four key evolution strategies: protein engineering, pegRNA modifications, accessory protein recruitment, and paired pegRNA approaches are outlined. Further persistent challenges and outline possible refinements are discussed, highlighting how further innovations can expand PE's utility across diverse areas of research, biotechnology, and potential therapeutic interventions.
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Biolistic Delivery of CRISPR/Cas9 with Ribonucleoprotein Complex in Wheat.
The great advances in exploiting the CRISPR/Cas9 system are paving the way for targeted genome engineering in plants. Genome editing by direct delivery of CRISPR/Cas9 ribonucleoprotein complexes (RNPs) into plant cells reduces off-target mutations and avoids the integration of foreign DNA fragments, thus providing an efficient and accurate method for precision crop breeding. Here we describe an RNP-based genome editing protocol for wheat. The protocol covers the in vitro transcription of sgRNA, purification of Cas9 protein, biolistic delivery of CRISPR/Cas9 RNPs, and tissue culture procedures for regenerating testable seedlings.
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Gene therapy beats premature-aging syndrome in mice.
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