Gene Mutation Key to Infertility in Male Mice
If same defect exists in men, it could lead to new treatments, study says.
By Steven Reinberg
HealthDay Reporter
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(SOURCES: Yi Zhang, Ph.D., researcher, Howard Hughes Medical Institute, University of North Carolina School of Medicine, Chapel Hill; Oct. 17, 2007, Nature, online)
WEDNESDAY, Oct. 17 (HealthDay News) -- A defect in a gene that's essential for the formation of functioning sperm cells may cause infertility by preventing the head of sperm from being able to penetrate an egg.
The finding, by researchers at the University of North Carolina at Chapel Hill, was based on research with mice. But it might one day lead to treatments for infertility in men, the scientists said.
In experiments with mice that lacked the crucial gene, Jhdm2a, the scientists found that the rodents didn't produce many mature sperm cells, and the sperm that were produced had abnormally shaped heads and nonfunctioning tails.
"We found how the expression of genes that are important for the maturation of sperm is controlled," said lead researcher Yi Zhang, a professor of biochemistry and biophysics at the UNC School of Medicine. The Jhdm2a gene is responsible for packing DNA in the head of a sperm cell, making the head like a hard ball that can penetrate an egg, he explained.
Even though the study mice had a sex drive, they weren't able to impregnate female mice, Zhang said. "The sperm can't swim and cannot enter the egg," he said.
The findings were published online Oct. 17 in the journal Nature.
Because the Jhdm2a gene has an effect on the development of functional sperm, it might be a target for new infertility treatments for men, Zhang added. He and his colleagues are looking at infertility patients to see if the same mutation is present in human males. But it's still not clear if a mutation in the gene is to blame for infertility in men, he said.
"If we identify this mutation in infertile patients, then we may find a way to make the patient's sperm mature," Zhang said. "We don't know yet -- it's just a possibility," he added.
It appears that Jhdm2a plays an important role in the late stages of sperm cell development. The mice lacking this gene had smaller testes, low sperm count, were infertile, and their sperm had abnormally shaped heads and immotile tails, Zhang said.
More information
For more on infertility, visit the U.S. National Library of Medicine.
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