1. Department of Biological Sciences,
2. Department of Developmental Biology and Department of Genetics,
3. Department of Biochemistry,
4. Developmental Biology Program, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
5. Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.
6. Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
7. Stanford Genome Technology Center, 855 California Avenue, Palo Alto, CA 94306, USA.
8. Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA.