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Found: 26 165
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DNA polymerases in precise and predictable CRISPR/Cas9-mediated chromosomal rearrangements.
BACKGROUND: Recent studies have shown that, owning to its cohesive cleavage, Cas9-mediated CRISPR gene editing outcomes at junctions of chromosomal rearrangements or DNA-fragment editing are precise and predictable; however, the underlying mechanisms are poorly understood due to lack of suitable assay system and analysis tool. RESULTS: Here we developed a customized computer program to take account of staggered or cohesive Cas9 cleavage and to rapidly process large volumes of junctional sequencing reads from chromosomal rearrangements or DNA-fragment editing, including DNA-fragment inversions, duplications, and deletions. We also established a sensitive assay system using HPRT1 and DCK as reporters for cell growth during DNA-fragment editing by Cas9 with dual sgRNAs and found prominent large resections or long deletions at junctions of chromosomal rearrangements. In addition, we found that knockdown of PolQ (encoding Polθ polymerase), which has a prominent role in theta-mediated end joining (TMEJ) or microhomology-mediated end joining (MMEJ), results in increased large resections but decreased small deletions. We also found that the mechanisms for generating small deletions of 1bp and >1bp during DNA-fragment editing are different with regard to their opposite dependencies on Polθ and Polλ (encoded by the PolL gene). Specifically, Polθ suppresses 1bp deletions but promotes >1bp deletions, whereas Polλ promotes 1bp deletions but suppresses >1bp deletions. Finally, we found that Polλ is the main DNA polymerase responsible for fill-in of the 5' overhangs of staggered Cas9 cleavage ends. CONCLUSIONS: These findings contribute to our understanding of the molecular mechanisms of CRISPR/Cas9-mediated DNA-fragment editing and have important implications for controllable, precise, and predictable gene editing.
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CRISPR-Cas9 mediated knockout of the white gene in the bluetongue virus vector, Culicoides sonorensis (biting midge).
Culicoides biting midges are small blood feeding insects responsible for the transmission of important arthropod-borne viruses (arboviruses) such as bluetongue virus (BTV), Schmallenberg virus (SBV) and epizootic hemorrhagic disease virus (EHDV), which cause major losses to livestock production worldwide. Culicoides sonorensis is the primary vector of BTV in North America and one of the few Culicoides species to be colonised and reared in artificial conditions. Gene editing technology has been used to explore virus-vector interactions in other vector groups, particularly within mosquitoes. Despite the availability of a reference genome since 2018, to date there have been no reports of gene editing in C. sonorensis. Here, we report the first instance of gene editing in C. sonorensis, achieved by intrathoracic injection of adult females with Cas9 and sgRNAs targeting the white gene. We generated heritable mutations in the white gene which produced both white eye and red eye phenotypes and went on to establish a homozygous knockout line carrying a single mutation. We observed gene editing efficiencies of up to 12.3%, making this an efficient protocol for genetic manipulation of Culicoides biting midges, opening the door to functional genomics studies and the development of control strategies in these important and understudied disease vectors.
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Gene editing holds promise for babies with deadly immune disease.
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Gene editing staves off deafness in mice.
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High efficacy full allelic CRISPR/Cas9 gene editing in tetraploid potato.
CRISPR/Cas9 editing efficacies in tetraploid potato were highly improved through the use of endogenous potato U6 promoters. Highly increased editing efficiencies in the Granular Bound Starch Synthase gene at the protoplast level were obtained by replacement of the Arabidopsis U6 promotor, driving expression of the CRISPR component, with endogenous potato U6 promotors. This translated at the ex-plant level into 35% full allelic gene editing. Indel Detection Amplicon Analysis was established as an efficient tool for fast assessment of gene editing in complex genomes, such as potato. Together, this warrants significant reduction of laborious cell culturing, ex-plant regeneration and screening procedures of plants with high complexity genomes.
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The Potential Therapeutic Applications of CRISPR/Cas9 in the Treatment of Gastrointestinal Cancers.
Gastrointestinal (GI) cancer is one the most prevalent types of cancer. Despite current chemotherapy's success, patients with GI cancer continue to have a dismal outcome. The onset and progression of cancer are caused by alterations and the abnormal expression of several families of genes, like tumor-suppressor genes, oncogenes, and chemotherapy-resistant genes. The final purpose of tumor therapy is to inhibit cellular development by modifying mutations and editing the irregular expression of genes It has been reported that CDH1, TP53, KRAS, ARID1A, PTEN, and HLA-B are the commonly mutated genes in GI cancer. Gene editing has become one potential approach for cases with advanced or recurrent CRC, who are nonresponsive to conventional treatments and a variety of driver mutations along with progression cause GI progression. CRISPR/Cas9 technique is a reliable tool to edit the genome and understand the functions of mutations driving GI cancer development. CRISPR/Cas9 can be applied to genome therapy for GI cancers, particularly with reference to molecular-targeted medicines and suppressors. Moreover, it can be used as a therapeutic approach by knocking in/out multiple genes. The use of CRISPR/ Cas9 gene editing method for GI cancer therapy has therefore resulted in some improvements. There are several research works on the role of CRISPR/Cas9 in cancer treatment that are summarized in the following separate sections. Here, the use of CRISPR/Cas9-based genome editing in GI and the use of CRISPR/Cas9 is discussed in terms of Targeting Chemotherapy Resistance-related Genes like; KRAS, TP53, PTEN, and ARID1A.
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Strong and tunable anti-CRISPR/Cas activities in plants.
CRISPR/Cas has revolutionized genome engineering in plants. However, the use of anti-CRISPR proteins as tools to prevent CRISPR/Cas-mediated gene editing and gene activation in plants has not been explored yet. This study describes the characterization of two anti-CRISPR proteins, AcrIIA4 and AcrVA1, in Nicotiana benthamiana. Our results demonstrate that AcrIIA4 prevents site-directed mutagenesis in leaves when transiently co-expressed with CRISPR/Cas9. In a similar way, AcrVA1 is able to prevent CRISPR/Cas12a-mediated gene editing. Moreover, using a N. benthamiana line constitutively expressing Cas9, we show that the viral delivery of AcrIIA4 using Tobacco etch virus is able to completely abolish the high editing levels obtained when the guide RNA is delivered with a virus, in this case Potato virus X. We also show that AcrIIA4 and AcrVA1 repress CRISPR/dCas-based transcriptional activation of reporter genes. In the case of AcrIIA4, this repression occurs in a highly efficient, dose-dependent manner. Furthermore, the fusion of an auxin degron to AcrIIA4 results in auxin-regulated activation of a downstream reporter gene. The strong anti-Cas activity of AcrIIA4 and AcrVA1 reported here opens new possibilities for customized control of gene editing and gene expression in plants.
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Gene editing to improve legume-rhizobia symbiosis in a changing climate.
In the last three years, several gene editing techniques have been developed for both model and crop legumes. CRISPR-Cas9-based tools, in particular, are outpacing other comparable gene editing technologies used in legume hosts and their microbial symbionts to understand the molecular basis of symbiotic nitrogen-fixation. Gene editing has helped identify new gene functions, validate genetic screens, resolve gene redundancy, examine the role of tandemly duplicated genes, and investigate symbiotic signaling networks in non-model plants. In this review, we discuss the advances made in understanding the legume-rhizobia symbiosis through the use of gene editing and highlight studies conducted under varying environmental conditions. We reason that future climate-hardy legumes must be able to better integrate environmental signals with nitrogen fixation by fine-tuning long distance signaling, continuing to select efficient rhizobial partners, and adjusting their molecular circuitry to function optimally under variable light and nutrient availability and rising atmospheric carbon dioxide.
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Prime Editing for Precise Genome Engineering in Drosophila.
Editing the Drosophila genome is incredibly useful for gene functional analysis. However, compared to gene knockouts, precise gene editing is difficult to achieve. Prime editing, a recently described CRISPR/Cas9-based technique, has the potential to make precise editing simpler and faster, and produce less errors than traditional methods. Initially described in mammalian cells, prime editing is functional in Drosophila somatic and germ cells. Here, we outline steps to design, generate, and express prime editing components in transgenic flies. Furthermore, we highlight a crossing scheme to produce edited fly stocks in less than 3 months.
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Iterative, multiplexed CRISPR-mediated gene editing for functional analysis of complex protease gene clusters.
Elucidation of gene function by reverse genetics in animal models frequently is complicated by the functional redundancy of homologous genes. This obstacle often is compounded by the tight clustering of homologous genes, which precludes the generation of multigene-deficient animals through standard interbreeding of single-deficient animals. Here, we describe an iterative, multiplexed CRISPR-based approach for simultaneous gene editing in the complex seven-member human airway trypsin-like protease/differentially expressed in a squamous cell carcinoma (HAT/DESC) cluster of membrane-anchored serine proteases. Through four cycles of targeting, we generated a library of 18 unique congenic mouse strains lacking combinations of HAT/DESC proteases, including a mouse strain deficient in all seven proteases. Using this library, we demonstrate that HAT/DESC proteases are dispensable for term development, postnatal health, and fertility and that the recently described function of the HAT-like 4 protease in epidermal barrier formation is unique among all HAT/DESC proteases. The study demonstrates the potential of iterative, multiplexed CRISPR-mediated gene editing for functional analysis of multigene clusters, and it provides a large array of new congenic mouse strains for the study of HAT/DESC proteases in physiological and in pathophysiological processes.
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