1. Laboratory of Hormonal Regulations; Institute of Developmental Biology; Russian Academy of Science; 26 Vavilov Street Moscow 117808 Russia
2. Département de Neurobiologie des Signaux Intercellulaires; Institut des Neurosciences, CNRS URA 1488 Université P. et M. Curie; 7 Quai St Bernard F-75252 Paris Cedex 05 France