1. The Jackson Laboratory; 600 Main Street Bar Harbor ME 04609 USA
2. Department of Internal Medicine; Erasmus Medical Center; Postbus 2040 3000 CA Rotterdam The Netherlands
3. Section of General Internal Medicine; Boston University School of Medicine; 801 Massachusetts Ave, Crosstown Center Boston MA 02118 USA
4. The National Heart, Lung, and Blood Institute's Framingham Heart Study; 73 Mt. Wayte Ave, Suite 2 Framingham MA 01702-5827 USA
5. Population Sciences Branch; National Heart, Lung, and Blood Institute; Building 31, Room 5A52, 31 Center Drive MSC 2486 Bethesda MD 20892 USA