1. Unité mixte de recherche S949 Institut National de la Santé et de la Recherche Médicale, Université de Strasbourg, Etablissement Français du Sang-Alsace, Strasbourg, France;
2. Cell Microscopy Center, Department of Cell Biology and
3. Laboratory of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands; and
4. Department of Molecular Cell Biology, Utrecht University, Utrecht, The Netherlands