1. Department of Anatomy and Embryology, Faculty of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
2. Ph.D. Program in Human Biology, School of Integrative and Global Majors, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
3. Laboratory Animal Resource Center, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
4. Life Science Center, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
5. International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
6. Transborder Medical Research Center, Faculty of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan