Wellcome Trust Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7BN, UK, Institute for Molecular Medicine Finland, University of Helsinki, Helsinki 00290, Finland, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Oxford OX3 7LJ, UK, NIHR Oxford Biomedical Research Centre, OUH Trust, Oxford OX3 7LE, UK and Department of Statistics, University of Oxford, Oxford OX1 3TG, UK.