Mice were housed in a room with controlled temperature and maintained in a 12:12 h light:dark cycle, with ad libitum access to water and food. All experiments were performed in accordance with Swiss legislation and the European Community Council directive (86/609/EEC) for the care and use of laboratory animals and were approved by the Veterinarian Office of the canton of Vaud and a local ethics committee. Timed pregnant C57BL6/J mice were ordered from Charles River Laboratories (France).