1. Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
2. Center for Integrative Molecular Biosciences, The Scripps Research Institute, La Jolla, CA 92037
3. Department of Molecular and Cellular Pharmacology, University of California, San Francisco, San Francisco, CA 94143
4. Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94143