1. Wellcome Trust Centre for Stem Cell Research and Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK.
2. Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.
3. Stem Cell and Brain Research Institute, Inserm, Avenue Doyen Jean Lépine, Lyon U846, France.
4. CIMAR/CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas, Porto 4050-123, Portugal.