Correction to: Nature https://doi.org/10.1038/nature17950 Published online 20 April 2016

The authors wish to retract this article for the following reason: An institutional investigation has concluded that Figs. 1b and 2e are unreliable and that much of the additional data in the paper cannot be reliably verified from records. Together, these issues decrease confidence in the integrity of the experimental findings reported. The authors sincerely apologize to the scientific community for any confusion and any unintended harm derived from the publication of this paper. All authors agree to the retraction of this article.