CRISPR gene editing technique is probably safe, study confirms

As you were. In May, a study claimed that the revolutionary CRISPR gene editing technique can cause thousands of unwanted and potentially dangerous mutations. The authors called for regulators to reassess the safety of the technique. 

But doubts were raised about these claims from the very beginning, not least because it was a tiny study involving just three mice. Some critics have called for the paper to be withdrawn. Now a paper posted online on 5 July has proposed a simple and more plausible explanation for the controversial results. If it’s right, the authors of the original study were wrong.

“We strongly encourage the authors to restate the title and conclusions of their original paper or provide properly controlled experiments that can adequately support their claims,” write the team behind the new study. “Not doing so does a disservice to the field and leaves the misleading impression that the strong statements and recommendations found in their paper are adequately supported by the data presented.”

Tsang and colleagues assumed the three mice they studied were essentially genetically identical because their parents were very closely related, but the way the colony of mice was maintained means this was probably not the case, the team, which includes Luca Pinello of Harvard University, say.

This explanation makes sense for another reason, too. The shared mutations in the edited mice were nowhere near DNA sequences resembling the one were targeted for editing, Pinello and colleagues point out, so it’s far from clear why CRISPR would cause mutations in these same sites in two different mice.

“I agree the two mice are indeed more likely to be closely related,” says geneticist Gaetan Burgio of the Australian National University, one of the many critics of the original paper. He says its publication in a prominent journal was a failure of peer review.