In DepthBiology

‘Base editors’ open new way to fix mutations

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Science  27 Oct 2017:
Vol. 358, Issue 6362, pp. 432-433
DOI: 10.1126/science.358.6362.432

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CRISPR has vastly simplified the ability to edit DNA, but there's one thing this new technology is not particularly good at: fixing what are known as point mutations, the cause of many human genetic diseases. Now, two new papers, one in Science and the other in Nature, describe a tool called base editing that borrows heavily from CRISPR and excels at correcting the point mutations. CRISPR, adopted from a primitive immune system used by bacteria, cuts the DNA double helix, which is made up of the bases known in shorthand as A, C, T, and G. The cell repair process can then introduce errors that cripple genes. Researchers can also add DNA to CRISPR to, say, change one base to another. But CRISPR doesn't do this efficiently. Enter base pair editors, which chemically alter one base into another one without cutting the double helix. In the Science study, researchers describe a base editor for RNA that effectively changes A to G and the Nature paper reports how a DNA base editor does the same swap. About half of the point mutations associated with human diseases are linked to mutant As. The two new base editors add powerful additions to the first DNA base editor that was reported in 2016, which changed Cs in DNA to Ts.