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Fertility hopes raised as key to conception is discovered
– Reported April 17, 2014
The study was the first to identify a protein, named Juno after the Roman goddess of marriage and childbirth, that sits on the surface of the egg and is essential for sperm cells to latch on to.
Japanese scientists found the male equivalent on the surface of sperm in 2005, sparking a decade-long hunt for its “mate”.
Gavin Wright, from the Wellcome Trust Sanger Institute in Cambridgeshire, said: “We have solved a longstanding mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived. Without this essential interaction, fertilisation just cannot happen.”
Eggs that lack the Juno protein look normal but are impenetrable to sperm rendering them effectively sterile. Scientists believe that some cases of female infertility could be explained by women having an abnormal version of the Juno protein. If this were the case, conventional IVF would be no help, but a procedure called Intra-cytoplasmic sperm injection (ICSI) in which the sperm is directly injected into the egg should overcome the problem.
After the initial binding of sperm and egg, Juno bows out, becoming virtually undetectable after 40 minutes, the scientists found.
The discovery could lead to new contraceptive drugs or vaccines that work by blocking Juno or its interaction with Izumo1, an artificial sperm protein.
Allan Pacey, a fertility expert at the University of Sheffield, said that scientists are still “remarkably sketchy” about the key molecules involved in sperm and egg interactions. Dr Pacey said: “Yet the information could be immensely useful to help in the diagnosis of infertility but also in the design of new novel contraceptives for both humans and other animal species.
Dr Wright’s team first created Izumo1 after a Japanese marriage shrine. This was used like a metal detector to seek out binding partners on the surface of the egg. Juno was singled out as Izumo1’s “other half”.
The study, published in the journal Nature, showed that Juno is essential for fertilisation by engineering mice that produced eggs lacking the molecule. All the animals were infertile and unable to conceive, although they had normal mating behaviour. The molecule is also present on the surface of human egg cells and is likely to play a similar role.
About one in eight couples have trouble having children through natural conception. In about one third of these cases, there is no obvious cause for infertility, and for some of these couples even IVF does not work.
Despite the discovery of Juno, Nick Macklon, professor of obstetrics and gynaecology at the University of Southampton, added that, if the protein was confirmed in humans, it would likely only affect a small proportion of women.
SOURCE: http://www.theaustralian.com.au/news