1. Institute of Reproductive Sciences, College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, China
2. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
3. Department of Reproductive Medicine, Guangdong Women and Children Hospital, Guangzhou, China
4. Department of Reproductive Medicine, Peking University Shenzhen Hospital, Medical Center of Peking University, Shenzhen, Guangdong, China
5. Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA