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Professor El-Nasir Lalani at Hammersmith Hospital
"We examined 20 women"
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Friday, 27 April, 2001, 00:25 GMT 01:25 UK
Single gene 'may cause infertility'
The embryo must implant into the womb wall
A defect in just one gene could be a major cause of previously unexplained infertility suggest scientists at a London hospital.

When an egg is fertilised, the resulting embryo has to become implanted into the wall of the uterus, or womb, for a successful pregnancy to begin.

Women with a defective gene called MUC 1 may find this implantation process is far less likely to succeed.

This discovery that the size of a single gene could influence fertility is important and it should offer a potential target for new treatment

Professor Robert Winston, Hammersmith Hospital
The gene produces a "sticky" protein which may possibly help the egg attach itself to the womb.

If this protein is not present in sufficient quantities, it may mean that not only is she highly unlikely to get pregnant naturally, but also could find that IVF treatment draws a blank as well.

The study, published in the Lancet medical journal compared the structure of the gene in two groups of women, some of whom were normally fertile, and some whose infertility was suspected to be as a result of failure of the embryo to implant.

They found that, in the "infertile" group, the size of one part of the gene tended to be much smaller.

The finding has been hailed as "groundbreaking" by the team at the Hammersmith Hospital in London which produced it.

One in three unexplained

As many as a third of women attending IVF clinics have infertility which is unexplained, and success rates in IVF are still weighted against the couple in most cases.

Professor Robert Winston, director of research and development at the Hammersmith, said: "We have always suspected that genetic factors may be responsible for the high failure rates of IVF.

"This discovery that the size of a single gene could influence fertility is important and it should offer a potential target for new treatment.

"There is no doubt, however, that many more genes will be found which also influence the implanted embryo - and at the Hammersmith, we hope to take these findings further and investigate other factors which influence the success and failure of IVF."

Gene therapy

Another fertility expert, Stephen Smith, a professor of reproductive medicine at the University of Cambridge, said MUC 1 was the target of many research projects into unexplained fertility.

He said that a larger study would be needed to confirm whether MUC 1 defects were the main cause, or whether a wider variety of genes were implicated.

He said: "My experience would tell me that the latter was the case."

However, if strong candidate genes are tracked down, Professor Smith believes some form of gene therapy to alter the surface of the womb lining would be possible.

He said: "In theory, it could be a single shot treatment given on day 10 of the cycle - the effects would only be temporary, but that is all that is needed for successful pregnancy."

His research team at Cambridge is currently looking into the best ways of delivering gene therapies to the womb surface.

It has succeeded in producing encouraging changes in mice, although this technology has yet to be transferred into human trials.

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