1. Chair of Cell Morphology and Molecular Neurobiology, Ruhr-University Bochum,Building NDEF 05/339, Universitaetsstrasse 150, D-44780 Bochum, Germany.
2. GSF-Institute for Stem Cell Research, Ingolstädter Landstraße 1,D-85764 Neuherberg, Germany.
3. Institute of Physiology, University of Munich, Schillerstaße 46, D-80634 München, Germany.