About the Authors

Steven A Harvey

Affiliation Wellcome Trust/CR-UK Gurdon Institute and Department of Zoology, The University of Cambridge, Cambridge, United Kingdom

James C Smith

To whom correspondence should be addressed. E-mail: jim.smith@nimr.mrc.ac.uk

Affiliations Wellcome Trust/CR-UK Gurdon Institute and Department of Zoology, The University of Cambridge, Cambridge, United Kingdom , MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, United Kingdom

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

SAH and JCS conceived and designed the experiments. SAH performed the experiments. SAH and JCS wrote the paper.