Scientists in Mainz and Aachen have discovered a new mechanism that controls egg cell fertility and that might have future therapeutic potential. It was revealed by Professor Dr. Walter Stöcker of the Institute of Zoology at Johannes Gutenberg University Mainz (JGU) that the blood protein fetuin-B plays an important and previously unknown role in the fertilization of oocytes. Fetuin-B, first identified in the year 2000, is formed in the liver and secreted into the blood stream. During a joint research project with researchers at RWTH Aachen University headed by Professor Dr. Willi Jahnen-Dechent of the Helmholtz Institute for Biomedical Engineering, it was discovered that fetuin-B contributes to egg cell fertility by regulating the hardening of the protective zona pellucida of oocytes. The findings have recently been published in the scientific journal Developmental Cell.