The "Juno" protein is a recent breakthrough discovery that may hold the key to fertility treatments, according to researchers at the Wellcome Trust Sanger Institute.
The protein, named after the Roman Goddess of fertility, is a key ingredient during fertilization. It allows sperm to recognize an egg and thereby produce an embryo.
Another protein involved in this process was identified in 2005 by Japanese researchers who named it Izumo, after a Japanese marriage shrine. It is displayed on the sperm and hones in on an egg via a receptor. Until now, its egg counterpart was a mystery.
"We have solved a long-standing mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived," Dr. Gavin Wright, senior author from the Sanger Institute in Britain, said in a statement. "Without this essential interaction, fertilization just cannot happen. We may be able to use this discovery to improve fertility treatments and develop new contraceptives."
About one in eight American couples suffer from infertility, defined as being unable to conceive after one year of unprotected sex, according to the infertility association RESOLVE.
By recreating our essential moment of birth artificially, Japanese scientists unearthed the Juno-Izumo relationship. The team developed mice that lacked the Juno protein - rendering them infertile - and observed that their eggs did not fuse with normal sperm. Likewise, male mice without the Izumo protein could not consummate.
The journal Nature, in which the study was published, commented that the discovery makes the Juno-Izumo partnership "the first discovered in any organism to be essential to reproduction."
They also found that once fertilized, the egg sheds the Juno protein within 40 minutes so that no other sperm can penetrate it.
The finding has the potential to aid couples attempting in vitro fertilization (IVF), Wright explained, a costly and lengthy procedure. Researchers are now screening infertile women to understand whether defects in the Juno receptor are a cause of infertility. If so, a simple genetic screening test could help women having difficulty conceiving naturally find the appropriate treatment.
