1. Department of Histology and Cellular Biology, Graduate School of Medical Sciences, Kanazawa University , Kanazawa 920-8640 , Japan
2. Department of Gynecology and Obstetrics, Graduate School of Medical Sciences, Kyushu University , Fukuoka 812-8582 , Japan
3. Department of Microbiology and Molecular Genetics, University of California, Davis , Davis , CA 95616 , USA