1. Department of Medicine, University of Washington, Seattle, WA 98195–7720, USA.
2. Department of Pathology, University of Washington, Seattle, WA 98195–7720, USA.
3. Department of Biochemistry, University of Washington, Seattle, WA 98195–7720, USA.
4. Department of Orthopaedic Surgery and Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, MI 48109–0486, USA.
5. Children's Hospital and Regional Medical Center, Seattle, WA 98105, USA.