Research unlocks the secret life of sperm

Scientists have discovered a lock-and-key mechanism between sperm and egg cells, which may explain why some couples are unable to conceive through IVF. Photo / Nicola Topping

Many infertile couples could be spared the pain and expense of fruitless IVF treatments, thanks to the discovery of a lock-and-key mechanism between sperm and egg cells.

The research could explain why couples with no apparent reproductive problems are unable to conceive. More than 40,000 in vitro fertilisation cycles are prescribed in Britain each year, but only 10,000 births result.

In addition to the £5000 ($12,800) cost of each cycle, the couples face huge amounts of stress and can suffer severe depression and in some cases divorce.

"Our work has quite a lot of relevance for humans and society and one of the main ones is infertility," said Dr Martin Brinkworth, a member of the team at the universities of Bradford and Leeds that discovered the lock-and-key mechanism.

Some 15 per cent of couples have trouble conceiving, about half of them because the man has a problem. But in only one-third of cases is the cause obvious, such as a low sperm count. This leaves 2 per cent of the male population who are infertile for no discernible reason.

Dr David Miller at the University of Leeds thinks the secret could be that the genetic keys in their sperm don't quite fit their partners' locks.

If a test could identify these men, up to a quarter of women who have intrusive fertility checks would be spared the procedures. It could also sharply decrease the 75 per cent failure rate of IVF by filtering out male candidates who have no chance of success.

Although the egg and sperm each supply half the DNA for the new baby, the egg provides all the cellular support systems. Until now, it was thought that sperm simply delivered the father's DNA to the egg, leaving control and regulation of the process to the mother's DNA.

But the research by the Leeds-Bradford scientists, and parallel work by a US team at the University of Utah, has found that some genes are left exposed in sperm, allowing them to play an important role in the development of the embryo.

The lock-and-key mechanism could help to explain how closely related species maintain their separate identities.

The team speculates that this may have been the fate of prehistoric couplings between humans and their close cousins, Neanderthals, with incompatible keys and locks ensuring that any offspring would be unable to breed.

- INDEPENDENT