PreprintCited by 1,356CRISPR and Genetic EngineeringRNA regulation and diseaseRNA Interference and Gene Delivery

Analysis of off-target effects of CRISPR/Cas-derived RNA-guided endonucleases and nickases

Open access
Cho, Seung Woo, Kim, Sojung, Kim, Yongsub, Kweon, Jiyeon, Kim, Heon Seok, Bae, Sangsu, Kim, Jin-Soo·2014·Genome Research

Abstract

RNA-guided endonucleases (RGENs), derived from the prokaryotic adaptive immune system known as CRISPR/Cas, enable targeted genome engineering in cells and organisms. RGENs are ribonucleoproteins that consist of guide RNA and Cas9, a protein component originated from Streptococcus pyogenes. These enzymes cleave chromosomal DNA, whose sequence is complementary, to guide RNA in a targeted manner, producing site-specific DNA double-strand breaks (DSBs), the repair of which gives rise to targeted genome modifications. Despite broad interest in RGEN-mediated genome editing, these nucleases are limited by off-target mutations and unwanted chromosomal translocations associated with off-target DNA cleavages. Here, we show that off-target effects of RGENs can be reduced below the detection limits of deep sequencing by choosing unique target sequences in the genome and modifying both guide RNA and Cas9. We found that both the composition and structure of guide RNA can affect RGEN activities in cells to reduce off-target effects. RGENs efficiently discriminated on-target sites from off-target sites that differ by two bases. Furthermore, exome sequencing analysis showed that no off-target mutations were induced by two RGENs in four clonal populations of mutant cells. In addition, paired Cas9 nickases, composed of D10A Cas9 and guide RNA, which generate two single-strand breaks (SSBs) or nicks on different DNA strands, were highly specific in human cells, avoiding off-target mutations without sacrificing genome-editing efficiency. Interestingly, paired nickases induced chromosomal deletions in a targeted manner without causing unwanted translocations. Our results highlight the importance of choosing unique target sequences and optimizing guide RNA and Cas9 to avoid or reduce RGEN-induced off-target mutations.

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Crossref · 10.1101/gr.162339.113

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  • The specificity of Cas9 activity can be enhanced by extending or truncating sgRNAs.

    “accumulative evidence showed that the specificity of Cas9 activity can be enhanced by extending or truncating sgRNAs”

    From Off-target effects in CRISPR/Cas9 gene editing (2023) · cites this paper as Cho et al., 2014

    The Results section (‘Guide RNA structure’; page unavailable) reports that adding two guanine nucleotides to the 5′ end of sgRNAs improved discrimination of off-target sites in the tested guides. It does not show that truncating sgRNAs enhances specificity; the shorter GX19 guides were less discriminating in this comparison. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Applying truncated sgRNAs to paired Cas9 nickases achieves even more reduction of undesired mutagenesis.

    “Even more reduction of undesired mutagenesis is achieved when truncated sgRNAs are applied to paired Cas9 nickases”

    From Off-target effects in CRISPR/Cas9 gene editing (2023) · cites this paper as Cho et al., 2014

    The Results section (‘Paired Cas9 nickases’; page not provided) reports fewer detectable off-target indels with paired nickases than with Cas9 nucleases. The ‘Guide RNA structure’ section examines adding nucleotides to sgRNAs, not truncating them. Our copy does not show that truncated sgRNAs were applied to paired nickases or produced a further reduction. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Extra guanine nucleotides at the 5' end of sgRNAs may hinder the interaction between the Cas9/sgRNA complex and the DNA at off-target sites.

    “may hinder the interaction between the Cas9/sgRNA complex and the DNA at the off-target sites”

    From Off-target effects in CRISPR/Cas9 gene editing (2023) · cites this paper as Cho et al., 2014

    In Results > Guide RNA structure (page unavailable), adding two 5′ guanines improved discrimination of off-target sites, with indels barely detected at six of seven validated sites. The paper does not show that the guanines hinder Cas9/sgRNA binding to off-target DNA; it instead suggests possible effects on guide RNA stability, concentration, or secondary structure. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • Extra guanine nucleotides at the 5' end of sgRNAs are favored in T7-promoter driven transcription.

    “These extra guanine nucleotides are favored in T7-promoter driven transcription”

    From Off-target effects in CRISPR/Cas9 gene editing (2023) · cites this paper as Cho et al., 2014

  • Both the structure and composition of the guide RNA can affect the frequency of off-target effects.

    “First, both the structure and composition of the guide RNA can affect the frequency of off-target effects.50”

    From CRISPR-Cas9: a new and promising player in gene therapy (2015) · cites this paper as [50]

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Authors
Cho, S. W., Kim, S., Kim, Y., Kweon, J., Kim, H. S., Bae, S., & Kim, J.-S.
Affiliations
Seoul National University (KR)
Corresponding author
Kim, Jin-Soo
Venue
Genome Research
Published
2013-11-19
Volume
24
Issue
1
Pages
132-141
ISSN
1088-9051 (ISSN-L)
OpenAlex
W2105464583
Cited by
1,356
References
48
Citations by year
2026: 14 · 2025: 50 · 2024: 76 · 2023: 77 · 2022: 94 · 2021: 125 · 2020: 125 · 2019: 122 · 2018: 126 · 2017: 150 · 2016: 160 · 2015: 115 · 2014: 117 · 2013: 4
Type
posted content
Language
en
Open access
Locations
  • Genome Research (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc)
  • PubMed Central (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • HighWire Press Open Archive (submittedVersion)
  • Seoul National University Open Repository (Seoul National University) (submittedVersion)
  • Scholarworks@UNIST (Ulsan National Institute of Science and Technology) (submittedVersion, cc-by-nc)
Funders
  • National Research Foundation
  • National Research Foundation of Korea
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › CRISPR and Genetic Engineering
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › RNA regulation and disease
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › RNA Interference and Gene Delivery
Keywords
CRISPR/Cas9, RNA-guided endonuclease, off-target effects, Cas9 nickase, guide RNA design, single-strand breaks, targeted genome editing, chromosomal translocation, chromosomal deletion, Streptococcus pyogenes
MeSH terms
Base Sequence, Binding Sites, Chromosomes, Human, Deoxyribonuclease I, DNA, Endonucleases, HeLa Cells, Humans, Models, Genetic, Mutation, Genome, Human, K562 Cells, DNA Breaks, Double-Stranded, Genetic Loci, RNA, Small Untranslated, High-Throughput Nucleotide Sequencing, Exome, CRISPR-Cas Systems, CRISPR-Associated Proteins

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