1. Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, UK.
2. Department of Zoology, University of Cambridge, Cambridge, UK.
3. Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK.
4. EMBL–European Bioinformatics Institute, Wellcome Genome Campus, Cambridge, UK.
5. Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, UK.
6. Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Cambridge, UK.
7. Wellcome Trust Centre for Stem Cell Research, University of Cambridge, Cambridge, UK.