There was an error published in Development 143, 648-657.

In the Materials and Methods section the murine Efnb2 gene mutation was incorrectly listed as Efnb2tm1And. The correct annotation for the floxed allele that we used in our experiments is Efnb2tm2And. This was a nomenclature error and does not affect the results or conclusions of the paper.

We thank Monika Tomczuk, scientific curator of Mouse Genome Informatics at The Jackson Laboratory, for alerting us to this mistake.

We apologise for any confusion that this error may have caused.