Precision CRISPR might be a little sloppier than we thought

A problem with old-fashioned CRISPR is that its approach to genome editing involves breaking DNA strands, which creates the potential for problematic off-target edits. That’s why base editing, the technology that can swap out single letters of the genomic alphabet without smashing DNA, has been widely heralded as a more precise alternative.

But as STAT’s Sharon Begley reports, new research suggests base editing may have off-target issues of its own. In a pair of papers, one in mice embryos and one in rice plants, scientists found that precisely altering single letters still led to hundreds of unintended edits elsewhere on the genome.

That doesn’t mean the whole approach is fatally flawed, scientists said. The rate of off-target mutations was something like 1 in 20 million, which could be small enough to be harmless. But it does suggest that even with the sharpest scissors possible, snipping the genome can be an imprecise endeavor.

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