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Found: 26 114
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Transgene-Killer-CRISPR version 2 (TKC2) eliminates occasional transgene escape by coupling with a RUBY reporter.
A critical step in generating gene-edited plants is the removal of CRISPR-related transgenes from T0 plants and their progenies, a process that is generally time-consuming and labour-intensive. We previously reported a Transgene Killer CRISPR (TKC) technology that enables self-elimination of transgenes after the targeted gene has been edited. However, we observed that a small number of T1 plants generated by TKC still retained the transgenes. Herein, we first integrated Cas9 and guide RNA (gRNA) with the RUBY reporter gene (RUBY-CRISPR) to monitor the Cas9/sgRNA expression and track the presence or absence of transgenes in the T0 generation and its progenies. We then combined the RUBY-CRISPR unit with several TKC variants to develop four RUBY-TKC (TKC2) systems including TKC2.1, TKC2.2, TKC2.3 and TKC2.4, to facilitate the elimination of escaped transgene plants. Compared to non-TKC, TKC alone and RUBY-CRISPR, our TKC2s were much more efficient in the generation of transgene-free edited progenies by up to 100% in the T0 generation. TKC2s not only omit the need for screening of the plants with transgenes in the T0 generation, but also enable visualisation of the escape of plants with transgenes in the following progenies. The TKC2 systems developed here provide straightforward yet highly effective approaches for the generation of transgene-free edited plants for either rice functional genomics or genetic improvement, with potential applications in gene editing of other crops.
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Peel-1 negative selection promotes screening-free CRISPR-Cas9 genome editing in Caenorhabditis elegans.
Improved genome engineering methods that enable automation of large and precise edits are essential for systematic investigations of genome function. We adapted peel-1 negative selection to an optimized Dual-Marker Selection (DMS) cassette protocol for CRISPR-Cas9 genome engineering in Caenorhabditis elegans and observed robust increases in multiple measures of efficiency that were consistent across injectors and four genomic loci. The use of Peel-1-DMS selection killed animals harboring transgenes as extrachromosomal arrays and spared genome-edited integrants, often circumventing the need for visual screening to identify genome-edited animals. To demonstrate the applicability of the approach, we created deletion alleles in the putative proteasomal subunit pbs-1 and the uncharacterized gene K04F10.3 and used machine vision to automatically characterize their phenotypic profiles, revealing homozygous essential and heterozygous behavioral phenotypes. These results provide a robust and scalable approach to rapidly generate and phenotype genome-edited animals without the need for screening or scoring by eye.
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CRISPRi-Based Dynamic Regulation of Hydrolase for the Synthesis of Poly-γ-Glutamic Acid with Variable Molecular Weights.
Poly-γ-glutamic acid (γ-PGA) is a decomposable polymer and has been useful in various industries. The biological functions of γ-PGA are closely linked with its molecular weight (MW). In this study, we established an efficient method to produce variable MWs of γ-PGA from renewable biomass (Jerusalem artichoke) by Bacillus amyloliquefaciens. First, a systematic engineering strategy was proposed in B. amyloliquefaciens to construct an optimal platform for γ-PGA overproduction, in which 24.95 g/L γ-PGA generation was attained. Second, 27.12 g/L γ-PGA with an MW of 20-30 kDa was obtained by introducing a γ-PGA hydrolase (pgdS) into the platform strain constructed above, which reveals a potential correlation between the expression level of pgdS and MW of γ-PGA. Then, a Clustered Regularly Interspaced Short Palindromic Repeats interference (CRISPRi) system was further designed to regulate pgdS expression levels, resulting in γ-PGA with variable MWs. Finally, a combinatorial approach based on three sgRNAs with different repression efficiencies was developed to achieve the dynamic regulation of pgdS and obtain tailor-made γ-PGA production in the MW range of 50-1400 kDa in one strain. This study illustrates a promising approach for the sustainable making of biopolymers with diverse molecular weights in one strain through the controllable expression of hydrolase using the CRISPRi system.
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Combination gene therapy for HIV using a conditional suicidal gene with CCR5 knockout.
BACKGROUND: Gene therapy approaches using hematopoietic stem cells to generate an HIV resistant immune system have been shown to be successful. The deletion of HIV co-receptor CCR5 remains a viable strategy although co-receptor switching to CXCR4 remains a major pitfall. To overcome this, we designed a dual gene therapy strategy that incorporates a conditional suicide gene and CCR5 knockout (KO) to overcome the limitations of CCR5 KO alone. METHODS: A two-vector system was designed that included an integrating lentiviral vector that expresses a HIV Tat dependent Thymidine Kinase mutant SR39 (TK-SR39) and GFP reporter gene. The second non-integrating lentiviral (NIL) vector expresses a CCR5gRNA-CRISPR/Cas9 cassette and HIV Tat protein. RESULTS: Transduction of cells sequentially with the integrating followed by the NIL vector allows for insertion of the conditional suicide gene, KO of CCR5 and transient expression of GFP to enrich the modified cells. We used this strategy to modify TZM cells and generate a cell line that was resistant to CCR5 tropic viruses while permitting infection of CXCR4 tropic viruses which could be controlled via treatment with Ganciclovir. CONCLUSIONS: Our study demonstrates proof of principle that a combination gene therapy for HIV is a viable strategy and can overcome the limitation of editing CCR5 gene alone.
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Ethical issues when modelling brain disorders innon-human primates.
Non-human animal models of human diseases advance our knowledge of the genetic underpinnings of disease and lead to the development of novel therapies for humans. While mice are the most common model organisms, their usefulness is limited. Larger animals may provide more accurate and valuable disease models, but it has, until recently, been challenging to create large animal disease models. Genome editors, such as Clustered Randomised Interspersed Palindromic Repeat (CRISPR), meet some of these challenges and bring routine genome engineering of larger animals and non-human primates (NHPs) well within reach. There is growing interest in creating NHP models of brain disorders such as autism, depression and Alzheimer's, which are very difficult to model or study in other organisms, including humans. New treatments are desperately needed for this set of disorders. This paper is novel in asking: Insofar as NHPs are being considered for use as model organisms for brain disorders, can this be done ethically? The paper concludes that it cannot. Notwithstanding ongoing debate about NHPs' moral status, (1) animal welfare concerns, (2) the availability of alternative methods of studying brain disorders and (3) unmet expectations of benefit justify a stop on the creation of NHP model organisms to study brain disorders. The lure of using new genetic technologies combined with the promise of novel therapeutics presents a formidable challenge to those who call for slow, careful, and only necessary research involving NHPs. But researchers should not create macaques with social deficits or capuchin monkeys with memory deficits just because they can.
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In Vitro Validation of Transgene Expression in Gene-Edited Pigs Using CRISPR Transcriptional Activators.
The use of CRISPR-Cas and RNA-guided endonucleases has drastically changed research strategies for understanding and exploiting gene function, particularly for the generation of gene-edited animal models. This has resulted in an explosion in the number of gene-edited species, including highly biomedically relevant pig models. However, even with error-free DNA insertion or deletion, edited genes are occasionally not expressed and/or translated as expected. Therefore, there is a need to validate the expression outcomes gene modifications in vitro before investing in the costly generation of a gene-edited animal. Unfortunately, many gene targets are tissue specific and/or not expressed in cultured primary cells, making validation difficult without generating an animal. In this study, using pigs as a proof of concept, we show that CRISPR-dCas9 transcriptional activators can be used to validate functional transgene insertion in nonexpressing easily cultured cells such as fibroblasts. This is a tool that can be used across disciplines and animal species to save time and resources by verifying expected outcomes of gene edits before generating live animals.
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Efficient mouse genome engineering by CRISPR-EZ technology.
CRISPR/Cas9 technology has transformed mouse genome editing with unprecedented precision, efficiency, and ease; however, the current practice of microinjecting CRISPR reagents into pronuclear-stage embryos remains rate-limiting. We thus developed CRISPR ribonucleoprotein (RNP) electroporation of zygotes (CRISPR-EZ), an electroporation-based technology that outperforms pronuclear and cytoplasmic microinjection in efficiency, simplicity, cost, and throughput. In C57BL/6J and C57BL/6N mouse strains, CRISPR-EZ achieves 100% delivery of Cas9/single-guide RNA (sgRNA) RNPs, facilitating indel mutations (insertions or deletions), exon deletions, point mutations, and small insertions. In a side-by-side comparison in the high-throughput KnockOut Mouse Project (KOMP) pipeline, CRISPR-EZ consistently outperformed microinjection. Here, we provide an optimized protocol covering sgRNA synthesis, embryo collection, RNP electroporation, mouse generation, and genotyping strategies. Using CRISPR-EZ, a graduate-level researcher with basic embryo-manipulation skills can obtain genetically modified mice in 6 weeks. Altogether, CRISPR-EZ is a simple, economic, efficient, and high-throughput technology that is potentially applicable to other mammalian species.
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Editing VEGFR2 Blocks VEGF-Induced Activation of Akt and Tube Formation.
PURPOSE: Vascular endothelial growth factor receptor 2 (VEGFR2) plays a key role in VEGF-induced angiogenesis. The goal of this project was to test the hypothesis that editing genomic VEGFR2 loci using the technology of clustered regularly interspaced palindromic repeats (CRISPR)-associated DNA endonuclease (Cas)9 in Streptococcus pyogenes (SpCas9) was able to block VEGF-induced activation of Akt and tube formation. METHODS: Four 20 nucleotides for synthesizing single-guide RNAs based on human genomic VEGFR2 exon 3 loci were selected and cloned into a lentiCRISPR v2 vector, respectively. The DNA fragments from the genomic VEGFR2 exon 3 of transduced primary human retinal microvascular endothelial cells (HRECs) were analyzed by Sanger DNA sequencing, surveyor nuclease assay, and next-generation sequencing (NGS). In the transduced cells, expression of VEGFR2 and VEGF-stimulated signaling events (e.g., Akt phosphorylation) were determined by Western blot analyses; VEGF-induced cellular responses (proliferation, migration, and tube formation) were examined. RESULTS: In the VEGFR2-sgRNA/SpCas9-transduced HRECs, Sanger DNA sequencing indicated that there were mutations, and NGS demonstrated that there were 83.57% insertion and deletions in the genomic VEGFR2 locus; expression of VEGFR2 was depleted in the VEGFR2-sgRNA/SpCas9-transduced HRECs. In addition, there were lower levels of Akt phosphorylation in HRECs with VEGFR2-sgRNA/SpCas9 than those with LacZ-sgRNA/SpCas9, and there was less VEGF-stimulated Akt activation, proliferation, migration, or tube formation in the VEGFR2-depleted HRECs than those treated with aflibercept or ranibizumab. CONCLUSIONS: The CRISPR-SpCas9 technology is a potential novel approach to prevention of pathologic angiogenesis.
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Highly efficient gene inactivation by adenoviral CRISPR/Cas9 in human primary cells.
Phenotypic assays using human primary cells are highly valuable tools for target discovery and validation in drug discovery. Expression knockdown (KD) of such targets in these assays allows the investigation of their role in models of disease processes. Therefore, efficient and fast modes of protein KD in phenotypic assays are required. The CRISPR/Cas9 system has been shown to be a versatile and efficient means of gene inactivation in immortalized cell lines. Here we describe the use of adenoviral (AdV) CRISPR/Cas9 vectors for efficient gene inactivation in two human primary cell types, normal human lung fibroblasts and human bronchial epithelial cells. The effects of gene inactivation were studied in the TGF-β-induced fibroblast to myofibroblast transition assay (FMT) and the epithelial to mesenchymal transition assay (EMT), which are SMAD3 dependent and reflect pathogenic mechanisms observed in fibrosis. Co-transduction (co-TD) of AdV Cas9 with SMAD3-targeting guide RNAs (gRNAs) resulted in fast and efficient genome editing judged by insertion/deletion (indel) formation, as well as significant reduction of SMAD3 protein expression and nuclear translocation. This led to phenotypic changes downstream of SMAD3 inhibition, including substantially decreased alpha smooth muscle actin and fibronectin 1 expression, which are markers for FMT and EMT, respectively. A direct comparison between co-TD of separate Cas9 and gRNA AdV, versus TD with a single "all-in-one" Cas9/gRNA AdV, revealed that both methods achieve similar levels of indel formation. These data demonstrate that AdV CRISPR/Cas9 is a useful and efficient tool for protein KD in human primary cell phenotypic assays. The use of AdV CRISPR/Cas9 may offer significant advantages over the current existing tools and should enhance target discovery and validation opportunities.
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Research advances on animal genetics in China in 2015.
Chinese scientists have made significant achievements in the field of animal genetics in 2015. Incomplete statistics show that among all the publications of 2015 involving nematode (Caenorhabditis elegans), fly (Drosophila melanogaster), zebrafish (Danio rerio), African clawed frog (Xenopus) or mice (Mus musculus), about 1/5 publications are from China. Many innovative studies were published in high-impact international academic journals by Chinese scientists, including the identification of a putative magnetic receptor MagR, the genetic basis for the regulation of wing polyphenism in the insect brown planthopper (Nilaparvata lugens), DNA N6-methyladenine (6mA) modification in the Drosophila genome, a novel molecular mechanism regarding the dendritic spine pruning and maturation in the mammals, the mechanism for the CREB coactivator CRTC2 in the regulation of hepatic lipid metabolism, the control of systemic inflammation by neurotransmitter dopamine, the role of Gasdermin protein family in triggering pyroptosis, a parvalbumin-positive excitatory visual pathway to trigger fear responses in mice, etc. Chinese scientists have also made important contributions in genome editing via TALEN or CRISPR/Cas system. According to incomplete statistics, more than 1/5 of the publications related to genome editing in 2015 are from China, where a variety of animals with different approaches were targeted, ranging from the worm to primates. Particularly, CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes was successfully achieved for the first time. China has been one of the leading countries in genome sequencing in recent years, and Chinese scientists reported the sequence and annotation of the genomes of several important animal species in 2015, including goose (Anser cygnoides), Schlegel's Japanese Gecko (Gekko japonicus), grass carp (Ctenopharyngodon idellus), large yellow croaker (Larimichthys crocea) and pig (Sus scrofa). They further analyzed the genome-wide genetic basis of the species-specific physiological and pathological characteristics as well as their adaptation to environmental conditions. In this review, we make a first attempt to summarize the research advances on animal genetics in China in 2015, with an emphasis on the achievements led by Chinese scientists and carried out in Chinese institutions. We will briefly discuss the significance of their research and contributions of Chinese scientists in animal genetics.
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