1. S. H. Tsang, J. Fisher, S. P. Goff, Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
2. P. Gouras and H. Kjeldbye, Edward Harkness Eye Institute, Department of Ophthalmology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
3. C. K. Yamashita and D. B. Farber, Jules Stein Eye Institute, Molecular Biology Institute and Department of Ophthalmology, UCLA School of Medicine, Los Angeles, CA 90095, USA.