Scientists have discovered a genetic mutation that could path the way for the development of new infertility treatments and also a male contraceptive pill. The mutation affects a protein called PLC zeta found in sperm which is responsible for activating an egg in the early stages of fertilisation. The study revealed that in cases where this protein was deactivated the sperm was not able to fertilise the egg.
The group of scientists, led by John Parrington at the University of Oxford, along with scientists from Ghent University in Belgium and the University of Massachusetts in the US, studied sperm from nine men who were involved in treatment for fertility problems. The men all required their sperm to be injected directly into eggs by a procedure called ICSI (intracytoplasmic sperm injection). The team, who were part funded by the Medical Research Council and other funding bodies in Belgium, published their findings in the journal Human Reproduction earlier this month.
'We have found that some men are infertile because their sperm fail to activate eggs,' said Kevin Coward of the Nuffield Department of Obstetrics and Gynaecology at the University of Oxford, who was involved in the study. 'Even though the sperm fuses with the egg, nothing happens. The sperm lack a proper functioning version of the PLC zeta protein involved,' he added.
The scientists discovered the mutation in an IVF patient at Ghent University Hospital. They then used mice to inject properly functioning PLC zeta protein into eggs. They found that the eggs were then 'activated', giving rise to hopes that such a technique could be used to treat fertility problems in males. Further studies would be necessary, however, to make the technique safe and effective for human use. 'This was a lab experiment and our method could not be used in a fertility clinic in exactly the same way,' said John Parrington, adding: 'But in the future, if we could produce the PLC protein artificially, we could stimulate egg activation in a completely natural way. For those couples going through IVF treatment where ICSI has failed, it could give them a chance of a baby.'
Whereas PLC zeta protein mutations may not be the reason for all male infertility, commentators say, the study does indicate that the malfunction is an underlying factor for men who struggle to fertilise eggs even when undergoing ICSI. It is believed that if the discovery leads to a treatment it could help up to 600 men per year. It could also lead to a male contraceptive technique if the PLC zeta could be blocked in fertile males, but such an effect would need to be proved fully reversible first.