1. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
2. University of Chinese Academy of Sciences, Beijing 100101, China
3. The Reproductive Medical Center, the First Affiliated Hospital, Zhengzhou University, Zhengzhou 450052, China
4. Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA