1. Center for Reproductive Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200135, China
2. Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Shanghai 200135, China
3. Center for Reproductive Sciences, University of California, San Francisco, CA 94143
4. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China