○Kayo Nishizawa¹, Natsuki Matsushita², Shigeki Kato¹, Yoshio Iguchi¹, Ryoji Fukabori¹, Kosei Takeuchi³, Yoshiki Miyasaka⁴, Tomoji Mashimo⁵, Kazuto Kobayashi¹ (1. Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University, Fukushima, Japan, 2. Division of Laboratory Animal Research, Aichi Medical University School of Medicine, Aichi 480-1195, Japan, 3. Department of Medical Cell Biology, Aichi Medical University School of Medicine, Aichi 480-1195, Japan, 4. Laboratory of Reproductive Engineering, Institute of Experimental Animal Sciences, Osaka University Medical School, Suita 565-0871, Japan, 5. Division of Animal Genetics, Laboratory Animal Research Center, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan)