1 Department of Maternal and Child Health Sciences, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, United Kingdom; Laboratoire de Biologic de la Differenciation et du Developpement, Universite Victor Segalen Bordeaux 2, EA 3674, 33076 Bordeaux Cedex, France; and INSERM U567, CNRS URM8104, Université Paris 5, Institut Cochin, Dpt. GDPM, 24 rue du Fg Saint Jacques, 75014 Paris, France