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Genetic Finding Called 'Breakthrough' for Male Infertility
Nov. 30, 1999 (Tuscaloosa, Ala.) -- Infertility is a growing worldwide problem, but researchers have taken a small step toward coping with it by identifying a specific mutation on a specific gene in the male Y chromosome, according to a new study published in the December issue of the medical journal Nature Genetics.
"Discovering this mutation is quite a feat,'' Robert Waterston, MD, tells WebMD. "It can be likened to finding a single misspelling in a multi-volume set of encyclopedias." Waterston, the chairman of the department of genetics of Washington University in St. Louis, is a leading gene researcher and was not involved in the new study.
"I would characterize the discovery as a breakthrough," adds Paul G. McDonough, MD, another expert consulted by WebMD.
"The finding is a first," McDonough points out. "It is a significant step forward in understanding the causes of male infertility." McDonough is a professor of obstetrics and gynecology, pediatrics, and endocrinology at the Medical College of Georgia in Augusta.
The discovery of the mutated gene was made by researchers affiliated with the Massachusetts Institute of Technology (MIT), St. Luke's Hospital in St. Louis, and Boston University's School of Medicine. The scientists compared the Y chromosomes of more than 575 infertile men and about 95 fertile men and identified two genes as being involved in sperm production. Then came the breakthrough. The researchers found a mutation on one of the genes belonging to a man with a severe fertility problem known as azoospermia -- he had absolutely no sperm in his semen.
The researchers then looked to see if the man's fertile brother also had the mutation. He didn't. That strongly suggested that the mutation, found on a gene identified as USP9Y, had caused the other brother's infertility. Further proof came when the scientists found the same mutation at the same USP9Y location on the Y chromosome of another azoospermic man.
"We have long known that faulty sperm production is caused by defects in the Y chromosome," Sherman Silber, MD, one of researchers, tells WebMD. "However, we didn't know the precise location of those defects.
"Now we know the precise location of one of those mutations. We believe there are more to be found," says Silber, who is director of the Infertility Center of St. Louis at St. Luke's Hospital. "We think that there are a whole variety of genes that regulate sperm production."
"If a man is missing just one gene, or if just one gene is defective, he may have low numbers of sperm in his semen. But if he is missing more of those genes, he will have even fewer sperm, perhaps none at all," explains Silber, who is also the author of the book How to Get Pregnant With the New Technology.
"Once we locate the other mutations, we can think of developing ways to repair the genes to make the men fertile again," Silber says. "That's the ultimate goal."
Vital Information:
- Researchers have identified a genetic mutation on the Y chromosome that causes a type of infertility called azoospermia, the absence of sperm in the semen.
- This is the first time a specific mutation has been identified.
- Scientists believe there are several other mutations that play a role in infertility.
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