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A CRISPR-Cpf1 system for efficient genome editing and transcriptional repression in plants.
Clustered regularly interspaced short palindromic repeats (CRISPR)-Cpf1 has emerged as an effective genome editing tool in animals. Here we compare the activity of Cpf1 from Acidaminococcus sp. BV3L6 (As) and Lachnospiraceae bacterium ND2006 (Lb) in plants, using a dual RNA polymerase II promoter expression system. LbCpf1 generated biallelic mutations at nearly 100% efficiency at four independent sites in rice T0 transgenic plants. Moreover, we repurposed AsCpf1 and LbCpf1 for efficient transcriptional repression in Arabidopsis, and demonstrated a more than tenfold reduction in miR159b transcription. Our data suggest promising applications of CRISPR-Cpf1 for editing plant genomes and modulating the plant transcriptome.
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Efficient somatic and germline genome engineering of Bactrocera dorsalis by the CRISPR/Cas9 system.
BACKGROUND: Bactrocera dorsalis (Hendel), a very destructive insect pest of many fruits and vegetables, is widespread in many Asian countries. To facilitate control of this pest, it is essential to investigate its genetics and gene function using targeted gene disruption. RESULTS: Here, we describe successful targeted mutagenesis of the white and transformer genes in B. dorsalis through use of the clustered regularly interspaced short palindromic repeats/CRISPR-associated 9 (CRISPR/Cas9) system. Co-injection of the white sgRNA and Cas9 mRNA into B. dorsalis embryos caused eye color change, and the white mutations in the germline were heritable. CRISPR-mediated knockout of the sex determination gene transformer (tra) in B. dorsalis resulted in a male-biased sex ratio and adult flies with abnormal outer and interior reproductive organs. Small indels and substitutions were induced by CRIRPR for both genes. CONCLUSION: Our data demonstrate that somatic and germline genome engineering of the pest B. dorsalis can be performed efficiently using the CRISPR/Cas9 system, opening the door to the use of the CRISPR-mediated method for functional annotations of genes in B. dorsalis and for its population control using, for example, such as gene drive. © 2018 Society of Chemical Industry.
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Cas11 augments Cascade functions in type I-E CRISPR system but is redundant for gene silencing and plasmid interference.
The structural and mechanistic complexity of Escherichia coli's type I Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated (CRISPR-Cas) system, compared with the multidomain, single effector protein-based type II systems, limits its application in genome editing and silencing. Despite the higher prevalence of the type I endogenous systems in bacteria, significant research has focused on improving the type II systems. While the type-I CRISPR system possesses several advantages over others, it may benefit from further studies to simplify the system for ease of use. To enable this, the dispensability of the type-I Cascade components (Cas8, Cas11, Cas7, Cas5 and Cas6) for genome editing and silencing applications was evaluated in vivo. We created deletion variants of each of the Cascade components and investigated their effects on gene silencing and plasmid interference in two genetically distinct E. coli lineages: BW25113, a K-12 strain that bears an endogenous, albeit repressed type I-E CRISPR system; and BL21, a natural mutant lacking the type I-E CRISPR-Cas system. Cas8, Cas7 and Cas5 were found to be indispensable for gene silencing and plasmid interference. Dispensability of Cas6, which is involved in crRNA maturation, was strain-dependent. Notably, Cas11, which has no definitive function assigned to it, was found to be dispensable for gene silencing and plasmid interference.
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Generation of Endogenously Tagged Membrane Trafficking Regulators Using CRISPR Genome Editing.
Vesicle trafficking entails packaging and transport of membrane-associated proteins to their target membranes, and recycling or degradation of endocytosed proteins. Biochemical and cell biological studies of vesicle trafficking often require the introduction of epitope tags or fluorescent protein markers for protein purification and tracking in cells. Previously, such tagging experiments in mammalian cells mainly used overexpression systems, which could lead to artifacts. Abnormally high expression levels also prevent us from studying individual vesicle trafficking events with precision. With the advent of CRISPR technologies, epitope tags and fluorescent proteins can now be introduced into endogenous proteins in almost any cell type that are proliferating in culture. This chapter describes approaches for inserting tags at the endogenous loci of genes, with the vesicle tethering protein complex, exocyst, as an example.
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Genome editors take on crops.
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Efficient generation of targeted and controlled mutational events in porcine cells using nuclease-directed homologous recombination.
BACKGROUND: Nuclease-based genome editing has rapidly sped the creation of new models of human disease. These techniques also hold great promise for the future of clinical xenotransplantation and cell-based therapies for cancer or immunodeficient pathology. However, to fully realize the potential of nuclease editing tools, the efficiency and precision of their application must be optimized. The object of this study was to use nonintegrating selection and nuclease-directed homologous recombination to efficiently control the genetic modification of the porcine genome. METHODS: Clustered randomly integrating spaced palindromic repeats and associated Cas9 protein (CRISPR/Cas9)-directed mutagenesis with a single-guide RNA target was designed to target the alpha-1,3-galactosyltransferase locus (GGTA1) of the porcine genome. A vector expressing a single-guide RNA, Cas9 protein, and green fluorescent protein was used to increase plasmid-delivered mutational efficiency when coupled with fluorescence sorting. Single and double-strand DNA oligonucleotides with a restriction site replacing the start codon were created with variable homology lengths surrounding the mutational event site. Finally, a transgene construct was flanked with 50 base pairs of homology directed immediately 5' to a nuclease cut site. These products were introduced to cells with a constant concentration of CRISPR/cas9 vector. Phenotype-specific mutational efficiency was measured by flow cytometer. Controlled homologous insertion was measured by Sanger sequence, restriction enzyme digest and flow cytometry. RESULTS: Expression of a fluorescence protein on the Cas9 vector functioned as a nonintegrating selection marker. Selection by this marker increased phenotype-silencing mutation rates from 3.5% to 82% (P = 0.0002). Insertion or deletion mutation increased from 11% to 96% (P = 0.0007). Co-transfection with homologous DNA oligonucleotides increased the aggregate phenotype-silencing mutation rates up to 22% and increased biallelic events. Single-strand DNA was twice as efficient as double-strand DNA. Furthermore, nuclease-mediated insertion by homology-directed repair successfully drove locus-specific transgene expression in the porcine genome. CONCLUSIONS: A nonintegrating selection strategy based on fluorescence expression can increase the mutational efficiency of the CRISPR/Cas9 system. The precision of this system can be increased by the addition of a very short homologous template sequence and can serve as a method for locus-specific transgene delivery. Together these strategies may be used to efficiently control mutational events. This system may be used to better use the potential of nuclease-mediated genomic editing.
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An Era of CRISPR/ Cas9 Mediated Plant Genome Editing.
Recently the engineered nucleases have revolutionized genome editing to perturb gene expression at specific sites in complex eukaryotic genomes. Three important classes of these genome editing tools are Moreover, the more recent type II Clustered Regularly Inter-spaced Short Palindromic Repeats/Crispr associated protein (CRISPR/Cas9) system has become the most favorite plant genome editing tool for its precision and RNA based specificity unlike its counterparts which rely on protein based specificity. Plasmid-mediated co-delivery of multiple sgRNAs and Cas9 to the Plant cell can simultaneously alter more than one target loci which enable multiplex genome editing. In this review, we discuss recent advancements in the CRISPR/ Cas9 technology mechanism, theory and its applications in plants and agriculture. We also suggest that the CRISPR/ Cas9 as an effective genome editing tool, has vast potential for crop improvement and studying gene regulation mechanism and chromatin remodeling.
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CRISPR-Cereal: a guide RNA design tool integrating regulome and genomic variation for wheat, maize and rice.
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Current situation of biofuel production and its enhancement by CRISPR/Cas9-mediated genome engineering of microbial cells.
Geopolitical and economic factors have motivated the scientific community to utilize renewable energy resources. In addition to the modifications in major steps and processes of biofuel production, manipulation of microbial genome engineering tools is essential in order to find sustainable solution of continuous depletion of fossil-fuels. Recently, the CRISPR (clustered regularly interspaced short palindromic repeat)/Cas9 (CRISPR-associated nuclease 9), a prokaryotic molecular immunity system, has emerged as a novel technology for targeted genomic engineering. This genetic machinery seems to be a groundbreaking discovery to engineer the microbial genomes for desired traits such as enhancing the biofuel tolerance, inhibitor tolerance and thermotolerance as well as modifying the cellulases and hemicelluloses enzymes. In this review, a summary of different generations of biofuels, integrated processes of bioconversion of raw materials into biofuels and role of microbes in biofuel production has been presented. However, the ultimate focus of the review is on major discoveries of CRISPR/Cas9-mediated genome editing in microorganisms and exploitation of these discoveries for enhanced biofuel production.
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Genome editing using CRISPR/Cas9-based knock-in approaches in zebrafish.
With its variety of applications, the CRISPR/Cas9 genome editing technology has been rapidly evolving in the last few years. In the zebrafish community, knock-out reports are constantly increasing but insertion studies have been so far more challenging. With this review, we aim at giving an overview of the homologous directed repair (HDR)-based knock-in generation in zebrafish. We address the critical points and limitations of the procedure such as cutting efficiency of the chosen single guide RNA, use of cas9 mRNA or Cas9 protein, homology arm size etc. but also ways to circumvent encountered issues with HDR insertions by the development of non-homologous dependent strategies. While imprecise, these homology-independent mechanisms based on non-homologous-end-joining (NHEJ) repair have been employed in zebrafish to generate reporter lines or to accurately edit an open reading frame by the use of intron-targeting modifications. Therefore, with higher efficiency and insertion rate, NHEJ-based knock-in seems to be a promising approach to target endogenous loci and to circumvent the limitations of HDR whenever it is possible and appropriate. In this perspective, we propose new strategies to generate cDNA edited or tagged insertions, which once established will constitute a new and versatile toolbox for CRISPR/Cas9-based knock-ins in zebrafish.
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