1. MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
2. Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 2XY, UK.
3. School of Life Science, University of Hamburg, Hamburg D-22527, Germany.
4. Edinburgh Cancer Research Centre, School of Molecular and Clinical Medicine,University of Edinburgh, MRC Human Genetics Unit Building, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
5. Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.