1. Division of Genetics and Genomics, Roslin Institute (Edinburgh), Midlothian EH25 9PS, Scotland
2. Aberdeen Centre for Energy Regulation and Obesity (ACERO), Energy Balance and Obesity Division, Rowett Research Institute, Aberdeen AB21 9SB, Scotland
3. School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, Scotland and
4. Sygen International PLC, Kingston Bagpuize, Oxfordshire OX13 5FE, England