Nature Cell Biology http://dx.doi.org/10.1038/ncb3554 (2017); published online 12 June 2017; corrected after print 21 June 2017

In the version of this Article originally published, the following affiliation was omitted for Sarah Wyck: Clinic of Reproductive Medicine, University of Zurich, Winterthurerstrasse 260, CH-8057 Zurich, Switzerland. This has been corrected in the online version of the Article.