Important Fertility Mechanism Discovered

Link:
http://www.biologynews.net/archives/2013/04/24/important_fertility_mechanism_discovered.html

Summary:
Scientists in Mainz and Aachen have discovered a new mechanism that controls fertility in egg cells.  This might have future therapeutic potential.  Professor Dr. Walter Stocker of the Institute of Zoology at Johannes Gutenberg University Mainz revealed that fetuin-B, a blood protein, plays an important role in the fertilization of oocytes.  Fetuin-B is formed in the liver and is secreted into the blood stream.  IT contributes to egg cell fertility by regulating the hardening of the protective zona pellucida of oocytes

The scientists at Aachen have found that female lice that lacked fetuin-B were infertile, even though their ovaries developed normally.  When their ovaries ere transplanted in wild-type mice with normal fetuin-B, fertility was restored.  This proved that it was not the ovaries, but fetuin-B that determined  if the mice were fertile or not.

The oocytes of humans and other mammals are surrounded by the zona pellucida, a protective envelope.  This hardens immediately after the fertilization of the egg by a sperm cell and prevents multiple fertilization, which leads to the death of the embryo in many mammals.  The hardening of the zona pelucida is caused by ovastacin, a proteolytic enzyme.  Some of the ovastacin seeps out of the egg, which would cause the zona to harden before it is fertilized.  Fetuin-B deactivates the ovastacin so that the zona does not harden and the oocytes can still be fertilized.

Themes of Nature of Science:
Science is collaborative- "During a joint research project..."
Science is based on evidence- "This demonstrates that it was not the ovaries themselves but the plasma protein fetuin-B that determined whether the mice were fertile of not."