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.
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| 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.
