1. Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
2. Drexel University College of Medicine, 60 N 36th Street, Philadelphia, PA 19104, USA
3. Broad Institute of Harvard and MIT, 7 Cambridge Center, Cambridge, MA 02142, USA
4. Harvard Stem Cell Institute, 7 Divinity Avenue, Cambridge, MA 02138, USA