1. Department of Pathology (J.A.E., A.T.C., P.W., M.M.M.), Texas 77030
2. Department of Molecular and Human Genetics (J.A.E., M.M.M.), Texas 77030
3. Genetics Institute (N.M.W.) Cambridge, Massachusetts 02140
4. Department of Cell Biology (M.M.M.) Baylor College of Medicine Houston, Texas 77030