1. Department of Developmental and Cell Biology; Sue and Bill Gross Stem Cell Research Center; University of California; Irvine CA USA
2. Jefferson Medical College; Thomas Jefferson University; Philadelphia PA USA
3. UMR 967; Cellules Souches et Radiations; CEA - INSERM - Universités Paris 7 et Paris 11; CEA/DSV/IRCM/SCSR/LRTS; Fontenay-aux-Roses Cedex France