1. Institute for Genomic Biology, Department of Cell and Developmental Biology, Department of Animal Sciences, and Department of Chemical and Molecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
2. State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Science, Beijing 100101, China
3. Stem Cell Program, Institute for Cell Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
4. Department of Cancer Biology, Vanderbilt University, Nashville, TN 37232