Nat. Cell Biol. 16, 526–534 (2014); published online 25 May 2014; corrected after print 30 May 2014

In the version of this Article originally published, the scale bars in Fig. 2c should have been labelled '3 mm'. In addition, a small red arrow indicating the location of the mutation was missing from Fig. 5c (shown below). These errors have now been corrected in the online versions of the Article.