1. Department of Animal Science, University of California, Davis, CA 95616, USA
2. Department of Clinical Sciences, Utrecht University, Yalelaan 108, 3584 CM Utrecht, The Netherlands
3. Department of Medical and Clinical Genetics, University of Helsinki, 00014 Helsinki, Finland
4. Department of Veterinary Biosciences, University of Helsinki, 00014 Helsinki, Finland
5. Folkhälsan Research Center, 00290 Helsinki, Finland
6. National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA