1. Diabetes Unit and Departments of Medicine and Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114,
2. Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
3. Program in Medical and Population Genetics, Whitehead/MIT Center for Genome Research, Cambridge, Massachusetts 02139
4. Divisions of Genetics and Endocrinology, Children's Hospital, Boston, Massachusetts 02114
5. Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114