Till now, it is a standard teaching that sperm moves ahead to fertilize ovum, but how it is attracted has been found recently.
Researchers at the Wellcome Trust Sanger Institute have discovered interacting proteins on the surface of the sperm and the egg essential for conjugation. The protein attract egg and sperm towards each other.
|English: Electron microscope image of sperm. (Photo credit: Wikipedia)|
Japanese researchers identified a protein in 2005 and named Izumo after a Japanese marriage shrine, which is displayed on the surface of sperm that recognizes egg. But its mate on the egg has remained a mystery till now.
The researchers have identified a single protein that paired with Izumo and is necessary for fertilization. The protein is named Juno after the Roman Goddess of fertility and marriage.
The team developed mice that lacked the Juno protein on the surface of their eggs. These mice were infertile and their eggs did not fuse with normal sperm, highlighting that the Juno protein is essential for fertility in female mice. In the same way, male mice lacking the Izumo protein are also infertile, highlighting its essential role in male fertility.
The team discovered that after about 40 minutes of the initial fertilization step, there is a sudden loss of the Juno protein from the surface of the egg. This may explain why the egg, once fertilized by the first sperm cell, shuts down its ability to recognize further sperm. This prevents the formation of embryos with more than one sperm cell that would otherwise have too many chromosomes and die.
The team is now screening infertile women to understand whether defects in the Juno receptor are a cause of infertility. If it is, then a simple genetic screening test could help inform the appropriate treatment for women struggling to conceive naturally by reducing the expense and stress often involved in assisted fertility treatments.
The article published in The ScienceDaily can be viewed here.