1. Department of Animal Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99164-7620
2. School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong
3. Laboratory for Biotechnology and Bioanalysis, Center for Reproductive Biology, Washington State University, Pullman, Washington 99164-7520
4. Department of Molecular and Cell Biology, University of California Berkeley, California 94720-3200