Andrea Brendolan, Elisabetta Ferretti, Valentina Salsi, Kelvin Moses, Susan Quaggin, Francesco Blasi, Michael L. Clearly and Licia Selleri Development132,3113-3126.

Fig. S1 in the supplementary material accompanying this paper was published incorrectly when the paper first appeared on-line.

This has now been rectified and we apologise to the authors and to readers for this mistake.