1. Joslin Diabetes Center (M.W., M.-E.P., C.B., A.B.G.), Boston, Massachusetts 02215;
2. Harvard Medical School (M.W., M.-E.P., A.B.G.), Harvard University, Boston, Massachusetts 02115;
3. Laboratory Genetic Metabolic Diseases (S.M.H.), Departments of Clinical Chemistry and Pediatrics, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands