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University of Toronto Team Isolates Gene Linked to Male Fertility; Will Male Birth-Control Pill Be Far Off?


A gene found in sperm cells originally believed to play a role in immunosuppression and cardiovascular disease may instead affect male fertility, according to a study conducted by an international team of researchers.

The research may lead to the development of molecular diagnostic tests that determine male fertility, as well as birth-control pills for men.

That the gene, Fkbp6, “would control male fertility was completely unexpected,” said Josef Penninger, professor of medical biophysics and immunology at the University of Toronto and senior author of the study. “We originally thought Fkbp6 was important for heart function but the only place we could find it was in sperm and oocytes.”

Penninger and his colleagues made their discovery when, after knocking out the gene in mice, they observed that all the sperm cells in male mice had died while oocytes in female mice appeared normal. The researchers noticed that their work “bore striking similarities” to work performed in Japan that looked at a mutation in rats that also caused aspermia.

Penninger, who later hooked up with that Japanese team as well as with researchers in the United States, later found that mice missing the Fkbp6 gene “com pletely lacked spermatids.”

“The deletion of the Fkbp6 gene was isolated as the cause for the infertility in mice,” he said in a statement. However, the male mice “showed normal sexual behavior and had normal levels of sex hormones.”

According to Penninger, “it would be interesting to test whether mutations in the Fkbp6 gene also account for human infertility” as well as infertility in mice and rats. He also speculated that the finding may lead to a male birth-control pill.

The study appears in the May 23 issue of Science.

Penninger’s group happened upon the link between the Fkbp6 gene and male fertility much the same way Pfizer researchers stumbled upon Viagra as a treatment for erectile dysfunction: by accident. Three years ago, he and his team began looking for evidence that the gene was implicated in cardiovascular disease.

“We found no link between this gene and heart disease but we did find that our male mice were unable to breed,” Penninger said. “When we investigated further, we found that the size of the testes of our mice were massively reduced and that they produced no sperm cells.”

Penninger told SNPtech Reporter that he next wants to find people who are infertile and see if they have mutations in this gene. “Of course if we find the mutation then it should be very easy to diagnose” infertility. “If somebody can come up with a drug to interfere with [Fkbp6] then you can selectively switch off sperm production without changing sex hormone profiles, or without changing sexual desire.”

It might be easier than he thinks: Penninger admitted to having missed the chance to patent the finding, opening the door for industry to take the first steps itself.

– KL

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