Sperm may 'sniff out' eggs

Human sperm use a chemical sensor to help them swim towards the egg, according to a new study. Scientists based at the Rohr University, Bochurn in Germany and the University of California in Los Angeles, US, showed that sperm have a protein on their surface that allows them to detect certain 'smells'. They also identified a chemical that stopped this smell receptor from working - findings that could lead to new fertility treatments and methods of contraception, says study author Richard Zimmer. The research, published in the journal Science, was described as 'a landmark piece of work' in an accompanying editorial.

The researchers found that the newly identified smell receptor, dubbed hOR17-4, triggers a series of events that may cause the sperm to move towards the egg. In the laboratory, sperm were drawn towards an artificial chemical called bourgeonal. 'If a natural equivalent to bourgeonal is, at least in part, responsible for successful pathfinding, or screening of fertile sperm, then it should be possible to use bourgeonal within IVF  treatments' said study author Marc Spehr. The study also showed that a chemical called undecanal stopped the sperm from responding to bourgeonal, a finding which could help in contraception research, speculated Spehr.

UK expert Allan Pacey called the work 'potentially very exciting', adding that the process of sperm transport to the egg was likely to involve a number of different mechanisms. Spehr also believes that other sperm cell receptors involved in chemoattraction will be uncovered, saying 'I don't expect nature to be dependent on one receptor type'.