Mice may hold the key to male Pill, say scientists

The prospect of a contraceptive pill for men has received a significant boost with a study proving that it is possible to generate male infertility without causing harmful side-effects such as loss of sex drive.

The prospect of a contraceptive pill for men has received a significant boost with a study proving that it is possible to generate male infertility without causing harmful side-effects such as loss of sex drive.

Scientists have been able to interfere with sperm production using a procedure that has no other repercussions on male behaviour or physical appearance, such as breast development, a common feature of prototype "male Pills".

They believe the findings will lead to new ways of tackling the problem of how to develop a male contraceptive pill which is both reversible and free of harmful side-effects.

A research team led by Professor Tony Hunter of the Salk Institute in La Jolla, California, discovered the new approach using mice with specific mutations for a gene involved in sending chemical messages to the sperm-making cells.

"The mutation appears to specifically knock out sperm formation without altering mating behaviour or feminising the mice physically. That's what makes it exciting as a potential target for a male contraceptive," Professor Hunter said.

The scientists said the single most important finding of the study, published in Nature Genetics journal was the lack of side-effects following the "treatment". "There seem to be no other observable effects of the mutation [in the gene] than the block of sperm maturation," said Peter Blume-Jensen, a researcher in Professor Hunter's laboratory.

The gene, called Kit/SCR-F, is responsible for producing a protein that "sits like a satellite dish" on the outer membrane of a cell issuing messages to the inside of the cell via a family of hormone-like chemicals. Removing the gene is lethal because of the range of vital activities it controls. But a mutation in part of it seems only to affect sperm production, says Dr Blume-Jensen.

Humans are likely to possess a similar gene, which gives scientists a possible target for designing a drug that temporarily blocks part of the Kit/SCR-F gene's function.

Any drug that mimics the effect of the mutation stands a good chance of being an effective yet safe contraceptive for men, Dr Blume-Jensen said.

"Provided that our findings translate to humans, such agents could be ideal male contraceptives," Dr Blume-Jensen said. Professor Hunter said it is the first gene defect to be found that interferes with sperm production without causing any other side-effects.

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