1. Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, California 90095
2. Molecular Biology Institute, University of California, Los Angeles, California 90095
3. Department of Biological Chemistry, University of California, Los Angeles, California 90095
4. Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, California 90095