1. Marshfield Clinic, Center for Human Genetics, and Department of Internal Medicine, 1000 N Oak Ave., Marshfield, WI 54449, USAE-mail:
2. Stanford University, Department of Genetics, 300 Pasteur Drive, L337, Stanford, CA 94305-5120, USA
3. Vanderbilt University, Center for Human Genetics Research, Department of Molecular Physiology & Biophysics, 519 Light Hall, Nashville, TN 37232, USA