[1] Hop Robert Debre, INSERM, U676, F-75019 Paris, France
[2] Univ London Imperial Coll Sci Technol & Med, Inst Reprod & Dev Biol, London W12 0NN, England
[3] Univ Calif San Francisco, Sch Med, Dept Pediat, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA