1. Institute of Human Genetics, University Medical Center 1 , 37073 Göttingen , Germany
2. Johann-Friedrich-Blumenbach Institute of Zoology and Anthropology, Göttingen Center of Molecular Biosciences, University of Göttingen 2 Department of Developmental Biology , , 37077 Göttingen , Germany
3. Institute for Developmental Biochemistry, University Medical Center 3 , 37077 Göttingen , Germany
4. Max Planck Institute for Biophysical Chemistry 4 Department of Molecular Developmental Biology , , 37077 Göttingen , Germany
5. Max Planck Institute for Biophysical Chemistry 5 Laboratory of Electron Microscopy , , 37077 Göttingen , Germany