scholarly journals Specificity Assessment of CRISPR Genome Editing of Oncogenic EGFR Point Mutation with Single-Base Differences

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 52 ◽  
Author(s):  
Taegeun Bae ◽  
Hanseop Kim ◽  
Jeong Hee Kim ◽  
Yong Jun Kim ◽  
Seung Hwan Lee ◽  
...  
Keyword(s):  
Genome Editing ◽  
Genetic Disorders ◽  
Point Mutations ◽  
Growth Factor Receptor ◽  
High Specificity ◽  
Complete Sequence ◽  
Single Base ◽  
Safety Issues ◽  
Ribonucleoprotein Complexes ◽  
Sequence Complementarity

In CRISPR genome editing, CRISPR proteins form ribonucleoprotein complexes with guide RNAs to bind and cleave the target DNAs with complete sequence complementarity. CRISPR genome editing has a high potential for use in precision gene therapy for various diseases, including cancer and genetic disorders, which are caused by DNA mutations within the genome. However, several studies have shown that targeting the DNA via sequence complementarity is imperfect and subject to unintended genome editing of other genomic loci with similar sequences. These off-target problems pose critical safety issues in the therapeutic applications of CRISPR technology, with particular concerns in terms of the genome editing of pathogenic point mutations, where non-mutant alleles can become an off-target with only a one-base difference. In this study, we sought to assess a novel CRISPR genome editing technique that has been proposed to achieve a high specificity by positioning the mismatches within the protospacer adjacent motif (PAM) sequence. To this end, we compared the genome editing specificities of the PAM-based and conventional methods on an oncogenic single-base mutation in the endothelial growth factor receptor (EGFR). The results indicated that the PAM-based method provided a significantly increased genome editing specificity for pathogenic mutant alleles with single-base precision.

scholarly journals Francisella novicida Cas9 interrogates genomic DNA with very high specificity and can be used for mammalian genome editing

2019 ◽  
Vol 116 (42) ◽  
pp. 20959-20968 ◽  
Author(s):  
Sundaram Acharya ◽  
Arpit Mishra ◽  
Deepanjan Paul ◽  
Asgar Hussain Ansari ◽  
Mohd. Azhar ◽  
...  
Keyword(s):  
Genome Editing ◽  
Genetic Disorders ◽  
High Specificity ◽  
Francisella Novicida ◽  
Guide Rna ◽  
Homology Directed Repair ◽  
Multiple Loci ◽  
Specificity Of Binding ◽  
Induced Pluripotent ◽  
Very High

Genome editing using the CRISPR/Cas9 system has been used to make precise heritable changes in the DNA of organisms. Although the widely used Streptococcus pyogenes Cas9 (SpCas9) and its engineered variants have been efficiently harnessed for numerous gene-editing applications across different platforms, concerns remain regarding their putative off-targeting at multiple loci across the genome. Here we report that Francisella novicida Cas9 (FnCas9) shows a very high specificity of binding to its intended targets and negligible binding to off-target loci. The specificity is determined by its minimal binding affinity with DNA when mismatches to the target single-guide RNA (sgRNA) are present in the sgRNA:DNA heteroduplex. FnCas9 produces staggered cleavage, higher homology-directed repair rates, and very low nonspecific genome editing compared to SpCas9. We demonstrate FnCas9-mediated correction of the sickle cell mutation in patient-derived induced pluripotent stem cells and propose that it can be used for precise therapeutic genome editing for a wide variety of genetic disorders.

scholarly journals Base editors: modular tools for the introduction of point mutations in living cells

2019 ◽  
Vol 3 (5) ◽  
pp. 483-491 ◽  
Author(s):  
Mallory Evanoff ◽  
Alexis C. Komor
Keyword(s):  
Synthetic Biology ◽  
Genome Editing ◽  
Genome Engineering ◽  
Point Mutations ◽  
Living Cells ◽  
Single Base ◽  
New Family ◽  
Alternative Techniques ◽  
Cas Proteins ◽  
Modular Nature

Base editors are a new family of programmable genome editing tools that fuse ssDNA (single-stranded DNA) modifying enzymes to catalytically inactive CRISPR-associated (Cas) endonucleases to induce highly efficient single base changes. With dozens of base editors now reported, it is apparent that these tools are highly modular; many combinations of ssDNA modifying enzymes and Cas proteins have resulted in a variety of base editors, each with its own unique properties and potential uses. In this perspective, we describe currently available base editors, highlighting their modular nature and describing the various options available for each component. Furthermore, we briefly discuss applications in synthetic biology and genome engineering where base editors have presented unique advantages over alternative techniques.

scholarly journals Efficient and Accurate Single-Base Genome Editing in Corynebacterium Glutamicum by Target-Mismatched CRISPR/Cpf1

2020 ◽  
Author(s):  
Hyun Ju Kim ◽  
Se Young Oh ◽  
Sang Jun Lee
Keyword(s):  
Corynebacterium Glutamicum ◽  
Genome Editing ◽  
Negative Selection ◽  
Stop Codon ◽  
Single Point ◽  
Point Mutations ◽  
Live Cells ◽  
Single Base ◽  
Base Editing ◽  
Target Dna

Abstract Background CRISPR/Cpf1 has emerged as a new CRISPR-based genome editing tool because, in comparison with CRIPSR/Cas9, it has a different T-rich PAM sequence to expand the target DNA sequence. Base editing in the microbial genome can be facilitated by oligonucleotide-directed mutagenesis (ODM) followed by negative selection with the CRISPR/Cpf1 system. However, single point mutations aided by Cpf1 negative selection have been rarely reported in C. glutamicum.Results This study aimed to introduce an amber stop codon in crtEb encoding lycopene hydratase, through ODM and Cpf1-mediated negative selection; deficiency of this enzyme causes pink coloration due to lycopene accumulation in Corynebacterium glutamicum. Consequently, on using double-, triple-, and quadruple-base-mutagenic oligonucleotides, 91.5–95.3% pink cells were obtained among the total live C. glutamicum cells. However, among the negatively selected live cells, 0.6% pink cells were obtained using single-base-mutagenic oligonucleotides, indicating that very few single-base mutations were introduced, possibly owing to mismatch tolerance. This led to the consideration of various target-mismatched crRNAs to prevent the death of single-base-edited cells. Consequently, we obtained 99.7% pink colonies after CRISPR/Cpf1-mediated negative selection using an appropriate single-mismatched crRNA. Furthermore, Sanger sequencing revealed that single-base mutations were successfully edited in the 99.7% of pink cells, while only two of nine among 0.6% of pink cells were accurately edited.Conclusions The present results indicate that the target-mismatched Cpf1 negative selection method is not only efficient in C. glutamicum, but also an accurate single-base genome editing method.

scholarly journals Modulating CRISPR-Cas genome editing using guide-complementary DNA oligonucleotides

2022 ◽  
Author(s):  
Thomas Swartjes ◽  
Peng Shang ◽  
Dennis van den Berg ◽  
Tim A. Kunne ◽  
Niels Geijsen ◽  
...  
Keyword(s):  
Genome Editing ◽  
Ex Vivo ◽  
Genetic Disorders ◽  
Complementary Dna ◽  
Dna Oligonucleotides ◽  
Ribonucleoprotein Complexes ◽  
Two Factors ◽  
Complementary Region ◽  
Human Genetic Disorders

CRISPR-Cas has revolutionized genome editing and has a great potential for applications, such as correcting human genetic disorders. To increase the safety of genome editing applications, CRISPR-Cas may benefit from strict control over Cas enzyme activity. Previously, anti-CRISPR proteins and designed oligonucleotides have been proposed to modulate CRISPR-Cas activity. Here we report on the potential of guide-complementary DNA oligonucleotides as controlled inhibitors of Cas9 ribonucleoprotein complexes. First, we show that DNA oligonucleotides down-regulate Cas9 activity in human cells, reducing both on and off-target cleavage. We then used in vitro assays to better understand how inhibition is achieved and under which conditions. Two factors were found to be important for robust inhibition: the length of the complementary region, and the presence of a PAM-loop on the inhibitor. We conclude that DNA oligonucleotides can be used to effectively inhibit Cas9 activity both ex vivo and in vitro.

scholarly journals Recruitment of DNA Repair MRN Complex by Intrinsically Disordered Protein Domain Fused to Cas9 Improves Efficiency of CRISPR-Mediated Genome Editing

Biomolecules ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 584 ◽  
Author(s):  
Nina Reuven ◽  
Julia Adler ◽  
Karin Broennimann ◽  
Nadav Myers ◽  
Yosef Shaul
Keyword(s):  
Dna Repair ◽  
Genome Editing ◽  
Genetic Defect ◽  
Point Mutations ◽  
Intrinsically Disordered Protein ◽  
Protein Domain ◽  
Mrn Complex ◽  
Intrinsically Disordered ◽  
Culture Cells ◽  
Ribonucleoprotein Complexes

CRISPR/Cas9 is a powerful tool for genome editing in cells and organisms. Nevertheless, introducing directed templated changes by homology-directed repair (HDR) requires the cellular DNA repair machinery, such as the MRN complex (Mre11/Rad50/Nbs1). To improve the process, we tailored chimeric constructs of Cas9, in which SpCas9 was fused at its N- or C-terminus to a 126aa intrinsically disordered domain from HSV-1 alkaline nuclease (UL12) that recruits the MRN complex. The chimeric Cas9 constructs were two times more efficient in homology-directed editing of endogenous loci in tissue culture cells. This effect was dependent upon the MRN-recruiting activity of the domain and required lower amounts of the chimeric Cas9 in comparison with unmodified Cas9. The new constructs improved the yield of edited cells when making endogenous point mutations or inserting small tags encoded by oligonucleotide donor DNA (ssODN), and also with larger insertions encoded by plasmid DNA donor templates. Improved editing was achieved with both transfected plasmid-encoded Cas9 constructs as well as recombinant Cas9 protein transfected as ribonucleoprotein complexes. Our strategy was highly efficient in restoring a genetic defect in a cell line, exemplifying the possible implementation of our strategy in gene therapy. These constructs provide a simple approach to improve directed editing.

scholarly journals Francisella novicidaCas9 interrogates genomic DNA with very high specificity and can be used for mammalian genome editing

2019 ◽  
Author(s):  
Sundaram Acharya ◽  
Arpit Mishra ◽  
Deepanjan Paul ◽  
Asgar Hussain Ansari ◽  
Mohd. Azhar ◽  
...  
Keyword(s):  
Genome Editing ◽  
Binding Affinity ◽  
Sickle Cell ◽  
Genetic Disorders ◽  
High Specificity ◽  
Gene Correction ◽  
Francisella Novicida ◽  
Multiple Loci ◽  
Specificity Of Binding ◽  
Very High

SUMMARYGenome editing using the CRISPR Cas9 system has been used to manipulate eukaryotic DNA and make precise heritable changes. Although the widely usedStreptococcus pyogenesCas9 (SpCas9) and its engineered variants have been efficiently harnessed for numerous gene-editing applications across different platforms, concerns remain, regarding their putative off targeting at multiple loci across the genome. Here we report thatFrancisella novicidaCas9 (FnCas9) shows a very high specificity of binding to its intended targets and negligible binding to off-target loci. The specificity is determined by its minimal binding affinity with DNA when mismatches to the target sgRNA are present in the sgRNA:DNA heteroduplex. FnCas9 produces staggered cleavage, higher HDR rates and very low non-specific genome editing compared to SpCas9. We demonstrate FnCas9 mediated correction of the sickle cell mutation in patient derived iPSCs and propose that it can be used for precise therapeutic genome editing for a wide variety of genetic disorders.SIGNIFICANCE STATEMENTTherapeutic genome editing has been significantly accentuated by the advent of CRISPR based gene correction. However, genomic off-targeting has been a major setback for clinical translation. Although high fidelity versions of Cas9 have been rationally designed, they recognize and bind to off-targets. In this study, we characterize a naturally occurring Cas9 fromFrancisella novicida(FnCas9) that shows negligible binding affinity to off targets differing by one or more mismatches, rendering it highly specific in target recognition and editing. We show that FnCas9 can direct both HDR and NHEJ mediated DNA repair, generates higher rate of HDR and negligible off-target editing. Finally we show its potential in therapeutic genome editing by correcting the sickle cell anemia mutation in patient derived iPSCs.

scholarly journals Whole-genome sequencing reveals rare off-target mutations in CRISPR/Cas9-edited grapevine

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xianhang Wang ◽  
Mingxing Tu ◽  
Ya Wang ◽  
Wuchen Yin ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Editing ◽  
Genome Sequencing ◽  
Plant Biotechnology ◽  
High Specificity ◽  
Fruit Trees ◽  
Whole Genome ◽  
Nucleotide Polymorphisms ◽  
Indel Mutation ◽  
Target Sites

AbstractThe CRISPR (clustered regularly interspaced short palindromic repeats)-associated protein 9 (Cas9) system is a powerful tool for targeted genome editing, with applications that include plant biotechnology and functional genomics research. However, the specificity of Cas9 targeting is poorly investigated in many plant species, including fruit trees. To assess the off-target mutation rate in grapevine (Vitis vinifera), we performed whole-genome sequencing (WGS) of seven Cas9-edited grapevine plants in which one of two genes was targeted by CRISPR/Cas9 and three wild-type (WT) plants. In total, we identified between 202,008 and 272,397 single nucleotide polymorphisms (SNPs) and between 26,391 and 55,414 insertions/deletions (indels) in the seven Cas9-edited grapevine plants compared with the three WT plants. Subsequently, 3272 potential off-target sites were selected for further analysis. Only one off-target indel mutation was identified from the WGS data and validated by Sanger sequencing. In addition, we found 243 newly generated off-target sites caused by genetic variants between the Thompson Seedless cultivar and the grape reference genome (PN40024) but no true off-target mutations. In conclusion, we observed high specificity of CRISPR/Cas9 for genome editing of grapevine.

scholarly journals Knock-in and precise nucleotide substitution using near-PAMless engineered Cas9 variants in Dictyostelium discoideum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuu Asano ◽  
Kensuke Yamashita ◽  
Aoi Hasegawa ◽  
Takanori Ogasawara ◽  
Hoshie Iriki ◽  
...  
Keyword(s):  
Genome Editing ◽  
Dictyostelium Discoideum ◽  
Streptococcus Pyogenes ◽  
Nucleotide Substitution ◽  
Point Mutations ◽  
Targeted Mutagenesis ◽  
Single Amino Acid ◽  
Specific Gene ◽  
Knock Out ◽  
Protospacer Adjacent Motif

AbstractThe powerful genome editing tool Streptococcus pyogenes Cas9 (SpCas9) requires the trinucleotide NGG as a protospacer adjacent motif (PAM). The PAM requirement is limitation for precise genome editing such as single amino-acid substitutions and knock-ins at specific genomic loci since it occurs in narrow editing window. Recently, SpCas9 variants (i.e., xCas9 3.7, SpCas9-NG, and SpRY) were developed that recognise the NG dinucleotide or almost any other PAM sequences in human cell lines. In this study, we evaluated these variants in Dictyostelium discoideum. In the context of targeted mutagenesis at an NG PAM site, we found that SpCas9-NG and SpRY were more efficient than xCas9 3.7. In the context of NA, NT, NG, and NC PAM sites, the editing efficiency of SpRY was approximately 60% at NR (R = A and G) but less than 22% at NY (Y = T and C). We successfully used SpRY to generate knock-ins at specific gene loci using donor DNA flanked by 60 bp homology arms. In addition, we achieved point mutations with efficiencies as high as 97.7%. This work provides tools that will significantly expand the gene loci that can be targeted for knock-out, knock-in, and precise point mutation in D. discoideum.

scholarly journals Versatile CRISPR/Cas9 Systems for Genome Editing in Ustilago maydis

2021 ◽  
Vol 7 (2) ◽  
pp. 149
Author(s):  
Sarah-Maria Wege ◽  
Katharina Gejer ◽  
Fabienne Becker ◽  
Michael Bölker ◽  
Johannes Freitag ◽  
...  
Keyword(s):  
Genome Editing ◽  
Cell Biology ◽  
Gene Deletion ◽  
Fluorescent Protein ◽  
Point Mutations ◽  
Model Organism ◽  
Ustilago Maydis ◽  
Genomic Locus ◽  
Targeted Gene Deletion ◽  
Molecular Cell Biology

The phytopathogenic smut fungus Ustilago maydis is a versatile model organism to study plant pathology, fungal genetics, and molecular cell biology. Here, we report several strategies to manipulate the genome of U. maydis by the CRISPR/Cas9 technology. These include targeted gene deletion via homologous recombination of short double-stranded oligonucleotides, introduction of point mutations, heterologous complementation at the genomic locus, and endogenous N-terminal tagging with the fluorescent protein mCherry. All applications are independent of a permanent selectable marker and only require transient expression of the endonuclease Cas9hf and sgRNA. The techniques presented here are likely to accelerate research in the U. maydis community but can also act as a template for genome editing in other important fungi.

scholarly journals The FGF/FGFR System in Breast Cancer: Oncogenic Features and Therapeutic Perspectives

Cancers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 3029
Author(s):  
Maria Francesca Santolla ◽  
Marcello Maggiolini
Keyword(s):  
Breast Cancer ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Kinase Inhibitors ◽  
Point Mutations ◽  
Growth Factor Receptor ◽  
Fibroblast Growth ◽  
Transduction Mechanisms ◽  
Molecular Landscape ◽  
Molecular Aberrations

One of the major challenges in the treatment of breast cancer is the heterogeneous nature of the disease. With multiple subtypes of breast cancer identified, there is an unmet clinical need for the development of therapies particularly for the less tractable subtypes. Several transduction mechanisms are involved in the progression of breast cancer, therefore making the assessment of the molecular landscape that characterizes each patient intricate. Over the last decade, numerous studies have focused on the development of tyrosine kinase inhibitors (TKIs) to target the main pathways dysregulated in breast cancer, however their effectiveness is often limited either by resistance to treatments or the appearance of adverse effects. In this context, the fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) system represents an emerging transduction pathway and therapeutic target to be fully investigated among the diverse anti-cancer settings in breast cancer. Here, we have recapitulated previous studies dealing with FGFR molecular aberrations, such as the gene amplification, point mutations, and chromosomal translocations that occur in breast cancer. Furthermore, alterations in the FGF/FGFR signaling across the different subtypes of breast cancer have been described. Next, we discussed the functional interplay between the FGF/FGFR axis and important components of the breast tumor microenvironment. Lastly, we pointed out the therapeutic usefulness of FGF/FGFR inhibitors, as revealed by preclinical and clinical models of breast cancer.

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