There were errors published in Development 143, 4474-4485.
In Figs 1A-D and 2A,B,H,I,J, the +/+ labels should have been +/–.
Owing to production errors, the wrong images were included as Figs 2B′, 3B,B′ and 5C′.
The online version of the article has been corrected accordingly. These changes have no impact on the results or the conclusions of the study.
We apologise to the authors and readers for this mistake.
© 2017. Published by The Company of Biologists Ltd