1. Tsinghua-Peking Center for Life Sciences, Beijing 100084, China.
2. Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China.
3. College of Animal Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
4. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
5. Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China.
6. Institute of Animal Science, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
7. College of Life Science, Northeast Agricultural University, Harbin 150030, China.