1. Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830
2. Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37235
3. Evergreen State College, Olympia, Washington 98505
4. Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709-2233