1. Department of Physiology and Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, Moran Eye Center and Program in Human Molecular Biology and Genetics, Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah 84132, and Laboratory of Bacterial Pathogenesis and Immunology, The Rockefeller University, New York, New York 10021