Correspondence to: h.clevers@hubrecht.eu
Correction to: The EMBO Journal (2012) 31, 2685–2696. doi:10.1038/emboj.2012.149
Since the publication of this paper, the authors have noticed errors in the labelling of Figure 4A.
The correct figure is shown on the next page and also in the online publication of this paper.
The authors apologize for any inconvenience caused.