Ovastacin cuts off sperm binding

Apr 02, 2012
A study in the Journal of Cell Biology describes how ovastacin helps egg cells avoid being fertilized by more than one sperm. In this image, ovastacin (red) localizes to secretory granules (green) in the cortex of an unfertilized egg. Credit: Burkart, A.D., et al. 2012. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201112094.

A study in The Journal of Cell Biology describes how a secreted enzyme helps egg cells avoid being fertilized by more than one sperm.

Because polyspermy disrupts , oocytes take several steps to ensure they only fuse with a single sperm. One key step is to prevent additional sperm from binding to the surface of an already-fertilized egg, a that involves the release of secretory granules and of a protein called ZP2, a component of the zona pellucida matrix that surrounds eggs. ZP2 is cleaved at a site targeted by the astacin family of metalloendoproteases – enzymes that cut proteins into smaller fragments. Researchers from the NIH's National Institute of Diabetes and Digestive and Kidney Diseases therefore investigated the function of ovastacin, an astacin family member expressed in oocytes.

Ovastacin localized to cortical granules that were exocytosed after fertilization, and recombinant ovastacin cleaved ZP2 when added to zonae pellucidae. Mice lacking ovastacin failed to cleave ZP2 after fertilization, allowing sperm to continue to bind to the surface of early embryos. Female mice lacking ovastacin had slightly fewer offspring than wild-type animals but otherwise appeared normal.

The researchers found that ovastacin targeted several sites in ZP2. Senior author Jurrien Dean now wants to investigate how this proteolysis blocks sperm binding, a critical question because the molecular interactions between sperm and remain unknown. He also wants to examine how ovastacin is packaged into oocyte cortical granules and to identify other components of these secretory organelles.

Explore further: How steroid hormones enable plants to grow

More information: Burkart, A.D., et al. 2012. J. Cell Biol. dx.doi.org/10.1083/jcb.201112094

add to favorites email to friend print save as pdf

Related Stories

Egg meets sperm: The female side of the story

Oct 21, 2010

Researchers at the Swedish medical university Karolinska Institutet have been able to describe the 3D structure of a complete egg receptor that binds sperm at the beginning of fertilization. The results, published in the ...

New requirements for male fertility

Apr 26, 2010

Two independent groups of researchers have identified distinct roles for two proteins in a family of proteins known as PLA2s as crucial for sperm function and fertility in mice. These data identify proteins that could underlie ...

Making sperm from stem cells in a dish

Aug 04, 2011

Researchers have found a way to turn mouse embryonic stem cells into sperm. This finding, reported in the journal Cell in a special online release on August 4th, opens up new avenues for infertility research and treatment. A Kyo ...

Researchers Develop Test to Identify 'Best' Sperm

May 20, 2010

(PhysOrg.com) -- Researchers at Yale School of Medicine have discovered a method to select sperm with the highest DNA integrity in a bid to improve male fertility. The method is comparable to that of the egg’s ...

Recommended for you

How steroid hormones enable plants to grow

19 hours ago

Plants can adapt extremely quickly to changes in their environment. Hormones, chemical messengers that are activated in direct response to light and temperature stimuli help them achieve this. Plant steroid ...

Surviving the attack of killer microbes

20 hours ago

The ability to find food and avoid predation dictates whether most organisms live to spread their genes to the next generation or die trying. But for some species of microbe, a unique virus changes the rules ...

Histones and the mystery of cell proliferation

20 hours ago

Before cells divide, they create so much genetic material that it must be wound onto spools before the two new cells can split apart. These spools are actually proteins called histones, and they must multiply ...

New discovery: Microbes create dripstones

Aug 18, 2014

According to new research humble, microscopic organisms can create dripstones in caves. This illustrates how biological life can influence the formation of Earth's geology - and the same may be happening ...

User comments : 0