Nat. Cell Biol. 14, 1336–1343 (2012); published online 25th November 2012; corrected online 30th November 2012

In the version of this Letter that was originally published, the affiliation of Jordi Molgó was erroneous. The correct affiliation is: CNRS, Institut de Neurobiologie Alfred Fessard FRC2118, Laboratoire de Neurobiologie et Développement, UPR 3294, 91198 Gif-sur-Yvette cedex, France.

This has now been corrected online.