1. P. De Camilli is at the Howard Hughes Medical Institute and in the Department of Cell Biology, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06510, USA.
2. S. D. Emr is at the Howard Hughes Medical Institute and in the Division of Cellular and Molecular Medicine, University of California at San Diego School of Medicine, La Jolla, CA 92093, USA.
3. P. S. McPherson is at the Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada.
4. P. Novick is in the Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.