PerspectiveGenome Editing

When genome editing goes off-target

See allHide authors and affiliations

Science  19 Apr 2019:
Vol. 364, Issue 6437, pp. 234-236
DOI: 10.1126/science.aax1827

You are currently viewing the summary.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution


Editing DNA in eukaryotic cells with CRISPR-based systems has revolutionized the genome engineering field. Cas (CRISPR-associated) endonucleases are directed to a particular location in the genome by a short guide RNA, providing an easily programmable strategy to target any section of DNA. As of now, two CRISPR-based approaches can introduce targeted, permanent edits. DNA cleavage with the Cas endonuclease facilitates small insertions or deletions of nucleotides that can disable the targeted gene (1). A second modified “base editor” system can generate precise single-base mutations in the targeted DNA (2). For both approaches, it is imperative that DNA modifications are made in the intended region (“on-target”) and not elsewhere in the genome (“off-target”). On pages 286, 289, and 292 of this issue, Wienert et al. (3), Zuo et al. (4), and Jin et al. (5), respectively, describe methods that identify off-target activities, which will be invaluable in therapeutic contexts as well as for stringent evaluation of future iterations of gene-editing tools.