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Found: 26 067
Page 43 of 1000-
Reply to: Atomic bomb and CRISPR gene editing technology.
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Scientists make precise gene edits to mitochondrial DNA for first time.
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Disruption of miRNA sequences by TALENs and CRISPR/Cas9 induces varied lengths of miRNA production.
MicroRNAs (miRNAs) are 20-24 nucleotides (nt) small RNAs functioning in eukaryotes. The length and sequence of miRNAs are not only related to the biogenesis of miRNAs but are also important for downstream physiological processes like ta-siRNA production. To investigate these roles, it is informative to create small mutations within mature miRNA sequences. We used both TALENs (transcription activator-like effector nucleases) and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) to introduce heritable base pair mutations in mature miRNA sequences. For rice, TALEN constructs were built targeting five different mature miRNA sequences and yielding heritable mutations. Among the resulting mutants, mir390 mutant showed a severe defect in the shoot apical meristem (SAM), a shootless phenotype, which could be rescued by the wild-type MIR390. Small RNA sequencing showed the two base pair deletion in mir390 substantially interfered with miR390 biogenesis. In Arabidopsis, CRISPR/Cas9-mediated editing of the miR160* strand confirmed that the asymmetric structure of miRNA is not a necessary determinant for secondary siRNA production. CRISPR/Cas9 with double-guide RNAs successfully generated mir160a null mutants with fragment deletions, at a higher efficiency than a single-guide RNA. The difference between the phenotypic severity of miR160a mutants in Col-0 versus Ler backgrounds highlights a diverged role for miR160a in different ecotypes. Overall, we demonstrated that TALENs and CRISPR/Cas9 are both effective in modifying miRNA precursor structure, disrupting miRNA processing and generating miRNA null mutant plants.
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An anti-CRISPR from a virulent streptococcal phage inhibits Streptococcus pyogenes Cas9.
The CRISPR-Cas system owes its utility as a genome-editing tool to its origin as a prokaryotic immune system. The first demonstration of its activity against bacterial viruses (phages) is also the first record of phages evading that immunity 1 . This evasion can be due to point mutations 1 , large-scale deletions 2 , DNA modifications 3 , or phage-encoded proteins that interfere with the CRISPR-Cas system, known as anti-CRISPRs (Acrs) 4 . The latter are of biotechnological interest, as Acrs can serve as off switches for CRISPR-based genome editing 5 . Every Acr characterized to date originated from temperate phages, genomic islands, or prophages 4-8 , and shared properties with the first Acr discovered. Here, with a phage-oriented approach, we have identified an unrelated Acr in a virulent phage of Streptococcus thermophilus. In challenging a S. thermophilus strain CRISPR-immunized against a set of virulent phages, we found one that evaded the CRISPR-encoded immunity >40,000× more often than the others. Through systematic cloning of its genes, we identified an Acr solely responsible for the abolished immunity. We extended our findings by demonstrating activity in another S. thermophilus strain, against unrelated phages, and in another bacterial genus immunized using the heterologous SpCas9 system favoured for genome editing. This Acr completely abolishes SpCas9-mediated immunity in our assays.
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Successful correction of factor V deficiency of patient-derived iPSCs by CRISPR/Cas9-mediated gene editing.
BACKGROUND: Factor V (FV) deficiency is a monogenic inherited coagulation disorder considered to be an ideal indication for gene therapy. To investigate the possibility of therapeutic application of genome editing, we generated induced pluripotent stem cells (iPSCs) from a FV-deficient patient and repaired the mutation of factor V gene (F5) using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9). METHODS: The patient's peripheral blood mononuclear cells were reprogrammed for iPSCs. The targeting vector was designed with homology arms against F5 containing the corrected sequence. Cas9 ribonucleoprotein (RNP) complex and targeting vector were electroporated into iPSCs. Gene-edited iPSCs were differentiated into hepatocyte-like cells (HLCs). RESULTS: The mutation of F5 in patient-derived iPSCs was repaired by CRISPR/Cas9. In concentrated culture supernatants of patient-derived iPS-HLCs, neither FV antigen nor activity was detected, while in those of gene-corrected iPS-HLCs, FV antigen and specific activity were 67.0 ± 13.1 ng/mL and 173.2 ± 41.1 U/mg, respectively. CONCLUSIONS: We successfully repaired the mutation of F5 using the CRISPR/Cas9 and confirmed the recovery of FV activity with gene-corrected iPS-HLCs. Gene-edited iPSCs are promising for elucidating the pathophysiology as well as for a modality of gene therapy.
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CRISPR therapy shows promise in Duchenne muscular dystrophy.
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CRISPR/Cas: a Nobel Prize award-winning precise genome editing technology for gene therapy and crop improvement.
Since it was first recognized in bacteria and archaea as a mechanism for innate viral immunity in the early 2010s, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) has rapidly been developed into a robust, multifunctional genome editing tool with many uses. Following the discovery of the initial CRISPR/Cas-based system, the technology has been advanced to facilitate a multitude of different functions. These include development as a base editor, prime editor, epigenetic editor, and CRISPR interference (CRISPRi) and CRISPR activator (CRISPRa) gene regulators. It can also be used for chromatin and RNA targeting and imaging. Its applications have proved revolutionary across numerous biological fields, especially in biomedical and agricultural improvement. As a diagnostic tool, CRISPR has been developed to aid the detection and screening of both human and plant diseases, and has even been applied during the current coronavirus disease 2019 (COVID-19) pandemic. CRISPR/Cas is also being trialed as a new form of gene therapy for treating various human diseases, including cancers, and has aided drug development. In terms of agricultural breeding, precise targeting of biological pathways via CRISPR/Cas has been key to regulating molecular biosynthesis and allowing modification of proteins, starch, oil, and other functional components for crop improvement. Adding to this, CRISPR/Cas has been shown capable of significantly enhancing both plant tolerance to environmental stresses and overall crop yield via the targeting of various agronomically important gene regulators. Looking to the future, increasing the efficiency and precision of CRISPR/Cas delivery systems and limiting off-target activity are two major challenges for wider application of the technology. This review provides an in-depth overview of current CRISPR development, including the advantages and disadvantages of the technology, recent applications, and future considerations.
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Super-precise new CRISPR tool could tackle a plethora of genetic diseases.
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Rapid construction of multiple sgRNA vectors and knockout of the Arabidopsis IAA2 gene using the CRISPR/Cas9 genomic editing technology.
IAA2 is a member of the Aux/IAA auxin responsive gene family in Arabidopsis thaliana. No iaa2 mutant has been reported until now, thus hindering its further mechanistic investigations. The normal genomic editing technology of CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) uses only a single guide RNA (sgRNA) to target one site in a specific gene, and the gene knockout efficiency is not high. Instead, multiple sgRNAs can target multiple sites; therefore, the efficiency may be improved. In the present investigation, we used the golden-gate cloning strategy and two rounds of PCR reactions to combine three sgRNAs in the same entry vector. The final expression vector was obtained by LR reactions with the destination vector containing the Cas9 expression cassette. Four out of the six sgRNAs were effective, and we also obtained a lot of insertion and deletion mutations. Compared with one sgRNA approach, multiple sgRNAs displayed higher gene-knockout efficiency and produced more germ-line mutants. Thus, we established a more rapid and efficient method and generated five mutants for further studies of IAA2 functions.
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Rapid Screening of CRISPR/Cas9-Induced Mutants Using the ACT-PCR Method.
The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system provides a technological breakthrough in targeted mutagenesis. However, a significant amount of time and cost is required to screen for the CRISPR/Cas9-induced mutants from a typically large number of initial samples. Here, we describe a cost-effective and sensitive screening technique based on conventional polymerase chain reaction (PCR), termed "annealing at critical temperature PCR" (ACT-PCR), for identifying mutants. ACT-PCR requires only a single PCR step followed by agarose gel electrophoresis. The simplicity of ACT-PCR makes it particularly suitable for rapid, large-scale screening of CRISPR/Cas9-induced mutants.
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