1 State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
2 Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China.
3 Howard Hughes Medical Institute, Department of Oncological Sciences and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
4 University of Chinese Academy of Sciences, Beijing 100049, China.