1. Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455.
2. Discovery Genomics, Inc., Minneapolis, MN 55413.
3. Department of Research Animal Resources, University of Minnesota, Minneapolis, MN 55455.
4. Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455.
5. Department of Pediatrics, University of California, San Francisco, CA 94143.