1. Burnham Institute for Medical Research, 10901 N. Torrey Pines Rd., La Jolla, California 92037
2. Molecular Pathology Graduate Program, University of California—San Diego, La Jolla, California 92093
3. Department of Molecular Neurobiology, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
4. Children's Hospital of Philadelphia, 517 Abramson Research Center, 3615 Civic Center Boulevard, Philadelphia, Pennsylvania 19104-4318