1. Department of Cell Biology, Institute of Anatomy, University of Aarhus, DK-8000 Aarhus C, Denmark;
2. Department of Oral Biology, Semmelweis University of Budapest, Budapest 1089, Hungary;
3. School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom; and
4. Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest 1083, Hungary