Chance discovery could lead to male pill

Scientists have discovered a genetic mutation that prevents the production of sperm, a chance find that could lead to the development of a male contraceptive pill.

Researchers were investigating the genetic basis of heart disease when they realised the mutation they were analysing in a strain of laboratory mice resulted in male sterility. When they eliminated the gene, called Fkbp6, in genetically engineering mice, the scientists found males were incapable of producing sperm, but egg production in females was unaffected.

Josef Penninger, Professor of Medical Biophysics at the University of Toronto, said that a mutation in the human equivalent of the Fkbp6 gene might be responsible for some cases of infertility in men. "That this gene would control male infertility was completely unexpected. We originally thought Fkbp6 was important for heart function, but the only place we could find it was in sperm and oocytes [egg cells]," Professor Penninger said. "When we investigated further, we found that the size of the testes in our mice were massively reduced and that they produced no sperm at all."

The study, published in this week's Science, found that without a functioning gene, the testes of male mice lacked any immature cells that eventually develop into fully-grown sperm. Professor Penninger said: "While our male mice showed normal sexual behaviour and had normal levels of sex hormones, they completely lacked sperm cells.

"So it's possible that Fkbp6 might be the perfect target for the development of a male birth-control pill."

Roughly 15 per cent of couples are childless because of infertility, but there are few instances of it being caused by genetic defects. Professor Penninger suggested that it might be possible to develop a test based on the Fkbp6 gene to see if it is responsible for some cases of male sterility.