K Ohata1,2, N Okamura3, M Kojima2, H Ya4,2. 1. University of Tsukuba, 305, Tsukuba, Ibaraki, Japan. 2. Animal Genome Research Group, National Institute of Animal Industry, Norin Kenkyu Danchi, P.O. Box 5, 305, Tsukuba, Ibaraki, Japan. 3. Institute of Basic Medical Sciences and Center for TARA (TARA researcher for Sakabe project), University of Tsukuba, 305, Tsukuba, Ibaraki, Japan. 4. Institute of Biologics, University of Tsukuba, 305, Tsukuba, Ibaraki, Japan.