1. U-368, INSERM (P.T., S.S.-M., G.L., P.C.) Biologie Moléculaire du Développement Ecole Normale Supérieure 75230 Paris, France
2. Laboratory of Molecular Biology (G.L.) Advanced Biotechnology Center-IST Genova, Italy
3. URA CNRS 1414 (A.T.) Ecole Normale Supérieure 75230 Paris, France
4. U-159, INSERM (D.G.) Centre Paul Broca 75014 Paris, France
5. Institut National de la Recherche Agronomique Physiologie de la Reproduction des Mammifères Domestiques (M.-A.D.) 37380 Nouzilly, France
6. Laboratory of Molecular Reproductive Biology and Medicine Department of Obstetrics and Gynecology (C.V.R.) University of Louisville Health Science Center Louisville, Kentucky 40292