1. Department of Molecular and Integrative Physiology (L.C., H.J., J.S., C.C.-S.), Ann Arbor, Michigan 48109
2. Program in Cellular and Molecular Biology (T.J.M., J.S.H.), Ann Arbor, Michigan 48109
3. Medical Scientist Training Program (J.S.H.), University of Michigan Medical School, Ann Arbor, Michigan 48109
4. and Department of Medicine (S.A.R.), McGill University Health Center, Montreal, Canada H3A 2A7