scholarly journals Points of View on the Tools for Genome/Gene Editing

2021 ◽  
Vol 22 (18) ◽  
pp. 9872
Author(s):  
Chin-Kai Chuang ◽  
Wei-Ming Lin
Keyword(s):  
Genome Editing ◽  
Dna Sequence ◽  
Nuclease Activity ◽  
Target Site ◽  
Homing Endonucleases ◽  
Null Mutant ◽  
Complementary Strand ◽  
Guide Rna ◽  
Strand Breakage

Theoretically, a DNA sequence-specific recognition protein that can distinguish a DNA sequence equal to or more than 16 bp could be unique to mammalian genomes. Long-sequence-specific nucleases, such as naturally occurring Homing Endonucleases and artificially engineered ZFN, TALEN, and Cas9-sgRNA, have been developed and widely applied in genome editing. In contrast to other counterparts, which recognize DNA target sites by the protein moieties themselves, Cas9 uses a single-guide RNA (sgRNA) as a template for DNA target recognition. Due to the simplicity in designing and synthesizing a sgRNA for a target site, Cas9-sgRNA has become the most current tool for genome editing. Moreover, the RNA-guided DNA recognition activity of Cas9-sgRNA is independent of both of the nuclease activities of it on the complementary strand by the HNH domain and the non-complementary strand by the RuvC domain, and HNH nuclease activity null mutant (H840A) and RuvC nuclease activity null mutant (D10A) were identified. In accompaniment with the sgRNA, Cas9, Cas9(D10A), Cas9(H840A), and Cas9(D10A, H840A) can be used to achieve double strand breakage, complementary strand breakage, non-complementary strand breakage, and no breakage on-target site, respectively. Based on such unique characteristics, many engineered enzyme activities, such as DNA methylation, histone methylation, histone acetylation, cytidine deamination, adenine deamination, and primer-directed mutation, could be introduced within or around the target site. In order to prevent off-targeting by the lasting expression of Cas9 derivatives, a lot of transient expression methods, including the direct delivery of Cas9-sgRNA riboprotein, were developed. The issue of biosafety is indispensable in in vivo applications; Cas9-sgRNA packaged into virus-like particles or extracellular vesicles have been designed and some in vivo therapeutic trials have been reported.

scholarly journals An improved method for precise genome editing in zebrafish using CRISPR-Cas9 technique

2021 ◽  
Author(s):  
Eugene V. Gasanov ◽  
Justyna Jędrychowska ◽  
Michal Pastor ◽  
Malgorzata Wiweger ◽  
Axel Methner ◽  
...  
Keyword(s):  
Genome Editing ◽  
High Efficiency ◽  
Target Site ◽  
Proof Of Concept ◽  
Intervention Site ◽  
End Joining ◽  
Guide Rna ◽  
Guide Rnas ◽  
Cas9 Nuclease ◽  
Non Homologous End Joining

AbstractCurrent methods of CRISPR-Cas9-mediated site-specific mutagenesis create deletions and small insertions at the target site which are repaired by imprecise non-homologous end-joining. Targeting of the Cas9 nuclease relies on a short guide RNA (gRNA) corresponding to the genome sequence approximately at the intended site of intervention. We here propose an improved version of CRISPR-Cas9 genome editing that relies on two complementary guide RNAs instead of one. Two guide RNAs delimit the intervention site and allow the precise deletion of several nucleotides at the target site. As proof of concept, we generated heterozygous deletion mutants of the kcng4b, gdap1, and ghitm genes in the zebrafish Danio rerio using this method. A further analysis by high-resolution DNA melting demonstrated a high efficiency and a low background of unpredicted mutations. The use of two complementary gRNAs improves CRISPR-Cas9 specificity and allows the creation of predictable and precise mutations in the genome of D. rerio.

scholarly journals Successful Transient Expression of Cas9 and Single Guide RNA Genes in Chlamydomonas reinhardtii

2014 ◽  
Vol 13 (11) ◽  
pp. 1465-1469 ◽  
Author(s):  
Wenzhi Jiang ◽  
Andrew J. Brueggeman ◽  
Kempton M. Horken ◽  
Thomas M. Plucinak ◽  
Donald P. Weeks
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Transient Expression ◽  
Gene Knockout ◽  
Nuclease Activity ◽  
Gene Replacement ◽  
Target Site ◽  
Gene Encoding ◽  
Content Type ◽  
Guide Rna ◽  
Eukaryotic Organisms

ABSTRACT The clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 system has become a powerful and precise tool for targeted gene modification (e.g., gene knockout and gene replacement) in numerous eukaryotic organisms. Initial attempts to apply this technology to a model, the single-cell alga, Chlamydomonas reinhardtii , failed to yield cells containing edited genes. To determine if the Cas9 and single guide RNA (sgRNA) genes were functional in C. reinhardtii , we tested the ability of a codon-optimized Cas9 gene along with one of four different sgRNAs to cause targeted gene disruption during a 24-h period immediately following transformation. All three exogenously supplied gene targets as well as the endogenous FKB12 (rapamycin sensitivity) gene of C. reinhardtii displayed distinct Cas9/sgRNA-mediated target site modifications as determined by DNA sequencing of cloned PCR amplicons of the target site region. Success in transient expression of Cas9 and sgRNA genes contrasted with the recovery of only a single rapamycin-resistant colony bearing an appropriately modified FKB12 target site in 16 independent transformation experiments involving >10 9 cells. Failure to recover transformants with intact or expressed Cas9 genes following transformation with the Cas9 gene alone (or even with a gene encoding a Cas9 lacking nuclease activity) provided strong suggestive evidence for Cas9 toxicity when Cas9 is produced constitutively in C. reinhardtii . The present results provide compelling evidence that Cas9 and sgRNA genes function properly in C. reinhardtii to cause targeted gene modifications and point to the need for a focus on development of methods to properly stem Cas9 production and/or activity following gene editing.

Robust Factor IX Expression Following ZFN-Mediated Genome Editing in An Adult Mouse Model of Hemophilia B

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 668-668
Author(s):  
Xavier M Anguela ◽  
Rajiv Sharma ◽  
Hojun Li ◽  
Virginia Haurigot ◽  
Anand Bhagwat ◽  
...  
Keyword(s):  
Mouse Model ◽  
Genome Editing ◽  
Partial Hepatectomy ◽  
Transgene Expression ◽  
Target Site ◽  
Factor Ix ◽  
Regulatory Control ◽  
Neonatal Mice ◽  
Proliferation Of Hepatocytes

Abstract Abstract 668 As a therapeutic strategy, site-specific modification of the genome has the potential to avoid some of the disadvantages of traditional gene replacement approaches such as insertional mutagenesis and lack of endogenous regulatory control of expression. We have recently reported that zinc finger nuclease (ZFN) driven gene correction can be achieved in vivo in a neonatal mouse model of hemophilia by combining AAV-mediated delivery of both the ZFNs and a Factor IX donor template with homology to the targeted F.IX gene (Li et al., Nature, 2011). The mouse model carries a mutant human F.IX mini-gene (hF9mut) knocked into the ROSA26 locus and ZFN-mediated cleavage followed by donor-dependent repair results in restoration of functional F.IX expression. AAV-ZFN and AAV-Donor vectors were administered to neonatal mice, where the rapid proliferation of hepatocytes in the growing animal may promote genome editing through homology directed repair (HDR). Here we sought to investigate whether ZFN-mediated genome editing is feasible in adult animals with predominantly quiescent hepatocytes. Tail vein injection of the AAV-ZFN and AAV-Donor, containing a promoterless wild type factor IX insert flanked by arms of homology to the target site, into adult (8 week old) mice (n=17) resulted in stable (>10wk) circulating F.IX levels of 730–1900 ng/mL (15-38% of normal), whereas mice receiving ZFN alone (n=9) exhibited F.IX levels below detection (<15 ng/mL). Co-delivery of AAV-Mock (luciferase expressing) & AAV-Donor (n=9), yielded <65 ng/mL F.IX. Importantly, mice lacking the hF9mut gene averaged less than 100 ng/mL after receiving AAV-ZFN and AAV-Donor (n=8), suggesting that F.IX expression was derived from on-target genome editing. To eliminate the potential for hF.IX expression resulting from episomal (non-integrated) AAV genomes we performed a two-thirds partial hepatectomy two days after AAV administration. Liver regeneration following hepatectomy is known to substantially reduce expression from non-integrated AAV genomes yet no significant differences in transgene expression were observed compared to non-hepatectomized mice: circulating F.IX levels in the AAV-ZFN + AAV-Donor group (n=13) ranged between 678–1240 ng/mL, whereas mice receiving ZFN alone (n=8) or Mock + AAV-Donor (n=8) had no detectable F.IX expression, or <100 ng/mL F.IX, respectively. Taken together, these data suggest that the F.IX expression in ZFN + Donor treated mice was derived from stable correction of the genome at the intended target site. In summary, we have shown that synchronized cell proliferation of hepatocytes, either in neonatal mice or following partial hepatectomy, is not necessary to achieve highly efficient genome editing and resultant high levels of transgene expression in vivo. These findings substantially expand the potential of ZFN-mediated genome editing as a therapeutic modality. Disclosures: Doyon: Sangamo Biosciences: Employment. Gregory:Sangamo Biosciences: Employment. Holmes:Sangamo Biosciences: Employment.

scholarly journals Nucleosomes inhibit target cleavage by CRISPR-Cas9 in vivo

2018 ◽  
Vol 115 (38) ◽  
pp. 9351-9358 ◽  
Author(s):  
Robert M. Yarrington ◽  
Surbhi Verma ◽  
Shaina Schwartz ◽  
Jonathan K. Trautman ◽  
Dana Carroll
Keyword(s):  
Genome Editing ◽  
Zinc Finger Nucleases ◽  
Yeast Genome ◽  
Target Sequence ◽  
Practical Applications ◽  
Guide Rna ◽  
Cas9 Protein ◽  
Wide Range

Genome editing with CRISPR-Cas nucleases has been applied successfully to a wide range of cells and organisms. There is, however, considerable variation in the efficiency of cleavage and outcomes at different genomic targets, even within the same cell type. Some of this variability is likely due to the inherent quality of the interaction between the guide RNA and the target sequence, but some may also reflect the relative accessibility of the target. We investigated the influence of chromatin structure, particularly the presence or absence of nucleosomes, on cleavage by the Streptococcus pyogenes Cas9 protein. At multiple target sequences in two promoters in the yeast genome, we find that Cas9 cleavage is strongly inhibited when the DNA target is within a nucleosome. This inhibition is relieved when nucleosomes are depleted. Remarkably, the same is not true of zinc-finger nucleases (ZFNs), which cleave equally well at nucleosome-occupied and nucleosome-depleted sites. These results have implications for the choice of specific targets for genome editing, both in research and in clinical and other practical applications.

scholarly journals All-in-One Adeno-associated Virus Delivery and Genome Editing by Neisseria meningitidis Cas9 in vivo

2018 ◽  
Author(s):  
Raed Ibraheim ◽  
Chun-Qing Song ◽  
Aamir Mir ◽  
Nadia Amrani ◽  
Wen Xue ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Neisseria Meningitidis ◽  
Genome Editing ◽  
Viral Vectors ◽  
Genome Engineering ◽  
Degradation Pathway ◽  
Type I ◽  
Guide Rna ◽  
Hereditary Tyrosinemia

AbstractClustered, regularly interspaced, short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) have recently opened a new avenue for gene therapy. Cas9 nuclease guided by a single-guide RNA (sgRNA) has been extensively used for genome editing. Currently, three Cas9 orthologs have been adapted for in vivo genome engineering applications: SpyCas9, SauCas9 and CjeCas9. However, additional in vivo editing platforms are needed, in part to enable a greater range of sequences to be accessed via viral vectors, especially those in which Cas9 and sgRNA are combined into a single vector genome. Here, we present an additional in vivo editing platform using Neisseria meningitidis Cas9 (NmeCas9). NmeCas9 is compact, edits with high accuracy, and possesses a distinct PAM, making it an excellent candidate for safe gene therapy applications. We find that NmeCas9 can be used to target the Pcsk9 and Hpd genes in mice. Using tail vein hydrodynamic-based delivery of NmeCas9 plasmid to target the Hpd gene, we successfully reprogrammed the tyrosine degradation pathway in Hereditary Tyrosinemia Type I mice. More importantly, we delivered NmeCas9 with its single-guide RNA in a single recombinant adeno-associated vector (rAAV) to target Pcsk9, resulting in lower cholesterol levels in mice. This all-in-one vector yielded >35% gene modification after two weeks of vector administration, with minimal off-target cleavage in vivo. Our findings indicate that NmeCas9 can facilitate future efforts to correct disease-causing mutations by expanding the targeting scope of RNA-guided nucleases.

scholarly journals In vivo CRISPR-Cas gene editing with no detectable genome-wide off-target mutations

2018 ◽  
Author(s):  
Pinar Akcakaya ◽  
Maggie L. Bobbin ◽  
Jimmy A. Guo ◽  
Jose M. Lopez ◽  
M. Kendell Clement ◽  
...  
Keyword(s):  
Genome Editing ◽  
Ex Vivo ◽  
Strong Support ◽  
Guide Rna ◽  
Genome Wide ◽  
Highly Sensitive ◽  
Further Development ◽  
Target Effects ◽  
Cas Gene

CRISPR-Cas genome-editing nucleases hold substantial promise for human therapeutics1–5 but identifying unwanted off-target mutations remains an important requirement for clinical translation6, 7. For ex vivo therapeutic applications, previously published cell-based genome-wide methods provide potentially useful strategies to identify and quantify these off-target mutation sites8–12. However, a well-validated method that can reliably identify off-targets in vivo has not been described to date, leaving the question of whether and how frequently these types of mutations occur. Here we describe Verification of In Vivo Off-targets (VIVO), a highly sensitive, unbiased, and generalizable strategy that we show can robustly identify genome-wide CRISPR-Cas nuclease off-target effects in vivo. To our knowledge, these studies provide the first demonstration that CRISPR-Cas nucleases can induce substantial off-target mutations in vivo, a result we obtained using a deliberately promiscuous guide RNA (gRNA). More importantly, we used VIVO to show that appropriately designed gRNAs can direct efficient in vivo editing without inducing detectable off-target mutations. Our findings provide strong support for and should encourage further development of in vivo genome editing therapeutic strategies.

scholarly journals Adenovirus Vectors Expressing Eight Multiplex Guide RNAs of CRISPR/Cas9 Efficiently Disrupted Diverse Hepatitis B Virus Gene Derived from Heterogeneous Patient

2021 ◽  
Vol 22 (19) ◽  
pp. 10570
Author(s):  
Yuya Kato ◽  
Hirotaka Tabata ◽  
Kumiko Sato ◽  
Mariko Nakamura ◽  
Izumu Saito ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Genome Editing ◽  
Adenovirus Vector ◽  
Target Sequence ◽  
Guide Rna ◽  
Guide Rnas ◽  
B Virus ◽  
X Gene

Hepatitis B virus (HBV) chronically infects more than 240 million people worldwide, causing chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Genome editing using CRISPR/Cas9 could provide new therapies because it can directly disrupt HBV genomes. However, because HBV genome sequences are highly diverse, the identical target sequence of guide RNA (gRNA), 20 nucleotides in length, is not necessarily present intact in the target HBV DNA in heterogeneous patients. Consequently, possible genome-editing drugs would be effective only for limited numbers of patients. Here, we show that an adenovirus vector (AdV) bearing eight multiplex gRNA expression units could be constructed in one step and amplified to a level sufficient for in vivo study with lack of deletion. Using this AdV, HBV X gene integrated in HepG2 cell chromosome derived from a heterogeneous patient was cleaved at multiple sites and disrupted. Indeed, four targets out of eight could not be cleaved due to sequence mismatches, but the remaining four targets were cleaved, producing irreversible deletions. Accordingly, the diverse X gene was disrupted at more than 90% efficiency. AdV containing eight multiplex gRNA units not only offers multiple knockouts of genes, but could also solve the problems of heterogeneous targets and escape mutants in genome-editing therapy.

scholarly journals A CRISPR Cas9 high-throughput genome editing toolkit for kinetoplastids

2017 ◽  
Vol 4 (5) ◽  
pp. 170095 ◽  
Author(s):  
Tom Beneke ◽  
Ross Madden ◽  
Laura Makin ◽  
Jessica Valli ◽  
Jack Sunter ◽  
...  
Keyword(s):  
Genome Editing ◽  
High Throughput ◽  
Large Scale ◽  
Leishmania Major ◽  
Fluorescent Protein ◽  
Genetic Manipulation ◽  
Gene Knockout ◽  
Guide Rna ◽  
Functional Studies

Clustered regularly interspaced short palindromic repeats (CRISPR), CRISPR-associated gene 9 (Cas9) genome editing is set to revolutionize genetic manipulation of pathogens, including kinetoplastids. CRISPR technology provides the opportunity to develop scalable methods for high-throughput production of mutant phenotypes. Here, we report development of a CRISPR-Cas9 toolkit that allows rapid tagging and gene knockout in diverse kinetoplastid species without requiring the user to perform any DNA cloning. We developed a new protocol for single-guide RNA (sgRNA) delivery using PCR-generated DNA templates which are transcribed in vivo by T7 RNA polymerase and an online resource (LeishGEdit.net) for automated primer design. We produced a set of plasmids that allows easy and scalable generation of DNA constructs for transfections in just a few hours. We show how these tools allow knock-in of fluorescent protein tags, modified biotin ligase BirA*, luciferase, HaloTag and small epitope tags, which can be fused to proteins at the N- or C-terminus, for functional studies of proteins and localization screening. These tools enabled generation of null mutants in a single round of transfection in promastigote form Leishmania major , Leishmania mexicana and bloodstream form Trypanosoma brucei ; deleted genes were undetectable in non-clonal populations, enabling for the first time rapid and large-scale knockout screens.

scholarly journals A single-plasmid approach for genome editing coupled with long-term lineage analysis in chick embryos

Development ◽  
2021 ◽  
pp. dev.193565
Author(s):  
Shashank Gandhi ◽  
Yuwei Li ◽  
Weiyi Tang ◽  
Jens B. Christensen ◽  
Hugo A. Urrutia ◽  
...  
Keyword(s):  
Genome Editing ◽  
Gene Function ◽  
Chick Embryos ◽  
Fluorescent Marker ◽  
Guide Rna ◽  
Single Plasmid ◽  
Lineage Analysis

An important strategy for establishing mechanisms of gene function during development is through mutation of individual genes and analysis of subsequent effects on cell behavior. Here, we present a single-plasmid approach for genome editing in chick embryos to study experimentally perturbed cells in an otherwise normal embryonic environment. To achieve this, we have engineered a plasmid that encodes Cas9 protein, gene-specific guide RNA (gRNA), and a fluorescent marker within the same construct. Using transfection- and electroporation-based approaches, we show that this construct can be used to perturb gene function in early embryos as well as human cell lines. Importantly, insertion of this cistronic construct into replication-incompetent avian (RIA) retroviruses allowed us to couple gene knockouts with long-term lineage analysis. We demonstrate the application of our newly-engineered constructs and viruses by perturbing β-catenin in vitro and Sox10, Pax6, and Pax7 in the neural crest, retina, neural tube and segmental plate in vivo, respectively. Together, this approach enables knocking out genes of interest in identifiable cells in living embryos and can be broadly applied to numerous genes in different embryonic tissues.

scholarly journals CRISPR/Cas “non-target” sites inhibit on-target cutting rates

2020 ◽  
Author(s):  
Eirik A. Moreb ◽  
Mitchell Hutmacher ◽  
Michael D. Lynch
Keyword(s):  
Genome Editing ◽  
Target Site ◽  
High Fidelity ◽  
List Type ◽  
Dependent Manner ◽  
Guide Rna ◽  
Protospacer Adjacent Motif ◽  
Target Sites ◽  
Dose Dependent ◽  
Target Activity

AbstractCRISPR/Cas systems have become ubiquitous for genome editing in eukaryotic as well as bacterial systems. Cas9 associated with a guide RNA (gRNA) searches DNA for a matching sequence (target site) next to a protospacer adjacent motif (PAM) and once found, cuts the DNA. The number of PAM sites in the genome are effectively a non-target pool of inhibitory substrates, competing with the target site for the Cas9/gRNA complex. We demonstrate that increasing the number of non-target sites for a given gRNA reduces on-target activity in a dose dependent manner. Furthermore, we show that the use of Cas9 mutants with increased PAM specificity towards a smaller subset of PAMs (or smaller pool of competitive substrates) improves cutting rates. Decreasing the non-target pool by increasing PAM specificity provides a path towards improving on-target activity for slower high fidelity Cas9 variants. These results demonstrate the importance of competitive non-target sites on Cas9 activity and, in part, may help to explain sequence and context dependent activities of gRNAs. Engineering improved PAM specificity to reduce the competitive non-target pool offers an alternative strategy to engineer Cas9 variants with increased specificity and maintained on-target activity.HighlightsThe pool of non-target PAM sites inhibit Cas9/gRNA on-target activitynon-target PAM inhibition is dose dependentnon-target PAM inhibition is a function of gRNA sequencenon-target PAM inhibition is a function of Cas9 levels

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