1. Department of Reproductive Medicine, Peking University Shenzhen Hospital, Shenzhen, Guangdong 518036, China
2. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
3. Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
4. University of Chinese Academy of Sciences, Beijing 100101, China