1. Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Box 7295, Chapel Hill, NC 27599, USA.
2. Howard Hughes Medical Institute, Department of Pharmacology, and Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Box 357370, Seattle, WA 98195, USA.
3. Department of Computer Science, University of North Carolina at Chapel Hill, Box 3175, Chapel Hill, NC 27599, USA.
4. Division of Dermatology, Department of Medicine, University of Washington School of Medicine, Box 358056, 815 Mercer Street, Seattle, WA 98109, USA.
5. Department of Physiology and Biophysics, University of Washington School of Medicine, Box 357370, Seattle, WA 98195, USA.