[1] Max Planck Inst Mol Biomed, Dept Cell & Dev Biol, D-48149 Munster, Germany
[2] Westphalian Wilhelms Univ Munster, Fac Med, Munster, Germany
[3] Ruhr Univ Bochum, Fac Med, Dept Anat & Mol Embryol, Bochum, Germany
[4] Med Univ Graz, Dept Blood Grp Serol & Transfus Med, Graz, Austria