[1] Univ Edinburgh, MRC Ctr Regenerat Med, Edinburgh EH16 4SB, Midlothian, Scotland
[2] Univ Edinburgh, Div Reprod & Dev Sci, Edinburgh EH16 4SB, Midlothian, Scotland
[3] Univ Edinburgh, MRC Human Reprod Sci Unit, Ctr Reprod Biol, Edinburgh EH16 4SB, Midlothian, Scotland
[4] Roslin Cells Ltd, Edinburgh, Midlothian, Scotland