1. Department of Anatomy, Histology and Embryology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China.
2. Shanghai Ji'Ai Genetics and IVF Institute, Shanghai, People's Republic of China.
3. National Population and Family Planning Key Laboratory of Contraceptive Drugs and Devices, Shanghai Institute of Planned Parenthood Research, Shanghai, People's Republic of China.
4. Department of Anatomy, The University of Hong Kong, Hong Kong SAR, People's Republic of China.
5. Department of Biological Sciences, University of Delaware, Newark, Delaware.