1. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
2. College of Life Science, Northeast Agricultural University, Harbin 150030, China
3. University of Chinese Academy of Sciences, Beijing 100101, China
4. College of Life Science, Qingdao Agricultural University, Qingdao 266109, China
5. Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA