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Protocol for CRISPR-Cas9 genome editing of a swine cell line via electroporation.
Genome editing technology is being used in animals for a variety of purposes, including improvement of animal and public health outcomes. Characterization of genome editing reagents and anticipated genomic alterations is an essential step toward the development of an edited animal. Here, we present a protocol for genome editing in the swine testicular (ST) cell line. We describe steps for evaluating CRISPR-Cas9 complex functionality in vitro, delivering editing molecules into cells by transfection, and assessing target editing via Sanger sequencing.
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Genome Editing and Hematologic Malignancy.
The modern genomic era has seen remarkable advancement in our understanding of the molecular basis for disease, yet translation of basic discoveries into new disease treatments has arguably lagged behind. Recently, breakthroughs in genome editing technologies have created hope for their potential to directly treat the genetic causes of disease. Like any therapeutic intervention, genome editing should be considered in light of its potential risks and benefits. In this review, we highlight the promise of genome editing therapies, as well as the conceptual and technical barriers to their clinical application, with a special emphasis on hematologic malignancies.
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Activation of homology-directed DNA repair plays key role in CRISPR-mediated genome correction.
Gene editing for the cure of inborn errors of metabolism (IEMs) has been limited by inefficiency of adult hepatocyte targeting. Here, we demonstrate that in utero CRISPR/Cas9-mediated gene editing in a mouse model of hereditary tyrosinemia type 1 provides stable cure of the disease. Following this, we performed an extensive gene expression analysis to explore the inherent characteristics of fetal/neonatal hepatocytes that make them more susceptible to efficient gene editing than adult hepatocytes. We showed that fetal and neonatal livers are comprised of proliferative hepatocytes with abundant expression of genes involved in homology-directed repair (HDR) of DNA double-strand breaks (DSBs), key for efficient gene editing by CRISPR/Cas9. We demonstrated the same is true of hepatocytes after undergoing a regenerative stimulus (partial hepatectomy), where post-hepatectomy cells show a higher efficiency of HDR and correction. Specifically, we demonstrated that HDR-related genome correction is most effective in the replicative phase, or S-phase, of an actively proliferating cell. In conclusion, this study shows that taking advantage of or triggering cell proliferation, specifically DNA replication in S-phase, may serve as an important tool to improve efficiency of CRISPR/Cas9-mediated genome editing in the liver and provide a curative therapy for IEMs in both children and adults.
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FXR1 regulates transcription and is required for growth of human cancer cells with TP53/FXR2 homozygous deletion.
Tumor suppressor p53 prevents cell transformation by inducing apoptosis and other responses. Homozygous TP53 deletion occurs in various types of human cancers for which no therapeutic strategies have yet been reported. TCGA database analysis shows that the TP53 homozygous deletion locus mostly exhibits co-deletion of the neighboring gene FXR2, which belongs to the Fragile X gene family. Here, we demonstrate that inhibition of the remaining family member FXR1 selectively blocks cell proliferation in human cancer cells containing homozygous deletion of both TP53 and FXR2 in a collateral lethality manner. Mechanistically, in addition to its RNA-binding function, FXR1 recruits transcription factor STAT1 or STAT3 to gene promoters at the chromatin interface and regulates transcription thus, at least partially, mediating cell proliferation. Our study anticipates that inhibition of FXR1 is a potential therapeutic approach to targeting human cancers harboring TP53 homozygous deletion.
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Simple, Efficient CRISPR-Cas9-Mediated Gene Editing in Mice: Strategies and Methods.
Genetic modification of almost any species is now possible using approaches based on targeted nucleases. These novel tools now bypass previous limited species windows, allowing precision nucleotide modification of the genome at high efficiency, rapidly and economically. Here we focus on the modification of the mouse genome; the mouse, with its short generation time and comparatively low maintenance/production costs is the perfect mammal with which to probe the genome to understand its functions and complexities. Further, using targeted nucleases combined with homologous recombination, it is now possible to precisely tailor the genome, creating models of human diseases and conditions directly and efficiently in zygotes derived from any mouse strain. Combined these approaches make it possible to sequentially and progressively refine mouse models to better reflect human disease, test and develop therapeutics. Here, we briefly review the strategies involved in designing targeted nucleases (sgRNAs) providing solutions and outlining in detail the practical processes involved in precision targeting and modification of the mouse genome and the establishing of new precision genetically modified mouse lines.
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Application of CRISPR/Cas9 Tools for Genome Editing in the White-Rot Fungus Dichomitus squalens.
Dichomitus squalens is an emerging reference species that can be used to investigate white-rot fungal plant biomass degradation, as it has flexible physiology to utilize different types of biomass as sources of carbon and energy. Recent comparative (post-) genomic studies on D. squalens resulted in an increasingly detailed knowledge of the genes and enzymes involved in the lignocellulose breakdown in this fungus and showed a complex transcriptional response in the presence of lignocellulose-derived compounds. To fully utilize this increasing amount of data, efficient and reliable genetic manipulation tools are needed, e.g., to characterize the function of certain proteins in vivo and facilitate the construction of strains with enhanced lignocellulolytic capabilities. However, precise genome alterations are often very difficult in wild-type basidiomycetes partially due to extremely low frequencies of homology directed recombination (HDR) and limited availability of selectable markers. To overcome these obstacles, we assessed various Cas9-single guide RNA (sgRNA) ribonucleoprotein (RNP) -based strategies for selectable homology and non-homologous end joining (NHEJ) -based gene editing in D. squalens. We also showed an induction of HDR-based genetic modifications by using single-stranded oligodeoxynucleotides (ssODNs) in a basidiomycete fungus for the first time. This paper provides directions for the application of targeted CRISPR/Cas9-based genome editing in D. squalens and other wild-type (basidiomycete) fungi.
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RNA and Protein Interactomes of an RNA-Binding Protein Tagged with FLAG Epitopes Using Combinatory Approaches of Genome Engineering and Stable Transfection.
To study the function of RNA-binding proteins (RBPs), an overexpression or knockout approach is generally used. However, as many RBPs are essential to cellular functions, the complete knockout of these proteins may be lethal to the cell. Overexpression of RBPs, on the other hand, may create an altered transcriptome and aberrant phenotypes that can mask their physiological function. Additionally, biochemical characterization of RBP often requires highly specific antibodies for efficient immunoprecipitation for downstream mass spectrometry or RNA footprinting profiling. To overcome these hurdles, we have developed a strategy to generate cellular systems either using a CRISPR-Cas9-mediated epitope tag knock-in approach or a two-step workflow to first stably express an exogenous Flag-tagged RBP and subsequently knockout the endogenous RBP using CRISPR-Cas9 gene editing. The generation of these cell lines will be beneficial for downstream RNA footprinting studies and mass spectrometry-mediated interactome studies.
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Falling giants and the rise of gene editing: ethics, private interests and the public good.
This paper considers the tensions created in genomic research by public and private for-profit ideals. Our intent is to strengthen the public good at a time when doing science is strongly motivated by market possibilities and opportunities. Focusing on the emergence of gene editing, and in particular CRISPR, we consider how commercialisation encourages hype and hope-a sense that only promise and idealism can achieve progress. At this rate, genomic research reinforces structures that promote, above all else, private interests, but that may attenuate conditions for the public good of science. In the first part, we situate genomics using the aphorism that 'on the shoulders of giants we see farther'; these giants are infrastructures and research cultures rather than individual 'heroes' of science. In this respect, private initiatives are not the only pivot for successful discovery, and indeed, fascination in those could impinge upon the fundamental role of public-supported discovery. To redress these circumstances, we define the extent to which progress presupposes research strategies that are for the public good. In the second part, we use a 'falling giant' narrative to illustrate the risks of over-indulging for-profit initiatives. We therefore offer a counterpoint to commercialised science, using three identifiable 'giants'-scientists, publics and cultures-to illustrate how the public good contributes to genomic discovery.
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Modeling suggests gene editing combined with vaccination could eliminate a persistent disease in livestock.
Recent breakthroughs in gene-editing technologies that can render individual animals fully resistant to infections may offer unprecedented opportunities for controlling future epidemics in farm animals. Yet, their potential for reducing disease spread is poorly understood as the necessary theoretical framework for estimating epidemiological effects arising from gene-editing applications is currently lacking. Here, we develop semistochastic modeling approaches to investigate how the adoption of gene editing may affect infectious disease prevalence in farmed animal populations and the prospects and time scale for disease elimination. We apply our models to the porcine reproductive and respiratory syndrome (PRRS), one of the most persistent global livestock diseases to date. Whereas extensive control efforts have shown limited success, recent production of gene-edited pigs that are fully resistant to the PRRS virus have raised expectations for eliminating this deadly disease. Our models predict that disease elimination on a national scale would be difficult to achieve if gene editing was used as the only disease control. However, from a purely epidemiological perspective, disease elimination may be achievable within 3 to 6 y, if gene editing were complemented with widespread and sufficiently effective vaccination. Besides strategic distribution of genetically resistant animals, several other key determinants underpinning the epidemiological impact of gene editing were identified.
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Gene editing of the thioester reductase step in the biosynthesis of lysergic acid amides.
Ergot alkaloids derived from lysergic acid are important in agriculture, as food and feed contaminants, and in medicine, as the foundation of several pharmaceuticals. The fungus Metarhizium brunneum makes several lysergic acid amides, with lysergic acid α-hydroxyethylamide (LAH) being produced in by far the highest concentration. The multifunctional enzyme lysergyl peptide synthetase 3 (Lps3) has multiple domains that play important roles in lysergic acid amide synthesis. We hypothesized a role for the reductase domain of Lps3 in liberating LAH from an enzyme-bound precursor and tested this hypothesis with CRISPR/Cas9-based gene editing experiments. We transformed M. brunneum with a Cas9/single guide RNA complex and a donor DNA that replaced the tyrosine at the active site of the reductase domain of Lps3 with a phenylalanine. Sanger sequencing of edited and wild-type genes demonstrated successful editing of the reductase domain without non-target mutations in Lps3. High performance liquid chromatography of the edited strain showed a significant reduction of LAH and accumulation of the precursor lysergic acid. The phenotype was similar when the edited allele of lpsC was in a wild-type background or in backgrounds with late pathway genes easO or easP knocked out, except no LAH was detectable when the edit was in the easO knockout background. The data demonstrate that the reductase domain plays a key role or roles in formation of LAH. The abundant lysergic acid accumulating in the mutants, as opposed to later pathway intermediates in LAH biosynthesis (such as lysergyl-alanine), indicated severe debilitation of Lps3. The data indicate a requirement for the reductase domain of Lps3 in synthesis of lysergic acid amides and demonstrate the feasibility of the CRISPR/Cas9-based approach for editing genes in Metarhizium species.
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