1. Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba 305-8575,Japan.
2. Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-0616, USA.
3. Department of Biochemistry, University of Calgary, Canada.
4. Department of Pathology and Laboratory Medicine, Children's Memorial Hospital,Feinberg School of Medicine, Northwestern University, Chicago, IL 60614-3394,USA.
5. Center for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba 305-8575, Japan.
6. Laboratory Animal Resource Center, University of Tsukuba, Tsukuba 305-8575,Japan.