1. Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109.
2. Division of Hematology, Department of Medicine, University of Washington, Seattle, WA 98195.
3. Division of Genetics, Department of Pediatrics and Developmental Medicine, University of Washington, Seattle, WA 98195.
4. Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA 98195.