1. Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
2. Department of Cell Biology, Scripps Research Institute, 10550 North Torrey Pines Road, SR11, La Jolla, CA 92037, USA.
3. Wadsworth Center, New York State Department of Health, Post Office Box 22002, Albany, NY 12201, USA.