The key to healthy sperm?

Laboratory mice that lacked the gene had a significantly lower sperm count and were infertile, researchers at the University of North Carolina at Chapel Hill discovered.

"Because this gene has a very specific effect on the development of functional sperm, it holds great potential as a target for new infertility treatments," Yi Zhang, a professor of biochemistry and biophysics at the university's school of medicine, said in a statement.

In an estimated 30 to 40% of couples who cannot conceive, it is the man who is infertile.

Zhang's study, which appears in the journal Nature, focused on the last stage of sperm cell formation known as spermiogenesis. During this phase, DNA is crammed into a tight ball at the head of the sperm, ensuring that it can successfully penetrate an egg.

Mice bred to lack a gene responsible for this process, produced few mature sperm, and the few that were produced had abnormally shaped heads and immobile tails.

"This gene is very important in controlling key genes that are involved in compacting the DNA," Zhang said in a telephone interview.

In the mutant mice, Zhang and colleagues detected a defect in sperm DNA packaging. The mice also had smaller testes, but Zhang said this was because the testes were not filled with sperm as they should be.

May be similar in men
He said more work needed to be done to discover whether this same defect causes infertility in men.

"The first thing we need to know is whether people have mutations of this gene," said Zhang, who plans to team up with researchers studying this infertility syndrome in humans.

Ultimately, he said this discovery could lead to the development of a drug that compensates for mutations in the gene.

"That possibility is there, but it is not going to happen tomorrow," Zhang said.

The research was funded by the Howard Hughes Medical Institute and the US National Institutes of Health. – (Reuters Health)

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October 2007