Chinese researchers have discovered a gene responsible for one form of male infertility, potentially paving the way for new treatments.
The scientists, led by Liu Mofang of the Institute of Biochemistry and Cell Biology in Shanghai, operating under the Chinese Academy of Sciences, found that mutations in the human Piwi gene hinder the development of sperm cells, causing infertility. They published their findings in the scientific journal Cell on May 25.
In China, there are more than 50 million infertile people. Approximately 1 percent of all Chinese men, and 10 to 20 percent of all infertile males, have azoospermia — a condition characterized by the absence of sperm in semen, and that in some cases is caused by Piwi gene mutations.
Liu told Sixth Tone that the mutations her team discovered in the human Piwi gene cause about 1 percent of azoospermia cases. But there are also other mutations in the human Piwi gene that could affect male fertility, and the scientists are working to solve the whole puzzle. “We estimate that at least 5 percent of azoospermia cases are affected by mutations of the human Piwi gene,” she said.
“It is an important discovery,” Zhang Feng, a professor at the Obstetrics and Gynecology Hospital of Fudan University, told Sixth Tone. “The discovery uncovers causes for male infertility that were not known to us before. But it will take some time before the discovery can be applied to clinical practice.” He added that compared to other research methods the genetic study of male infertility is more effective when it comes to early treatment and disease prediction.
Liu and her team started their research in 2011. They examined the DNA of 413 men with azoospermia for which no cause had been determined, and eventually found three patients with mutant Piwi genes.
The proteins for which the Piwi gene codes are known to be essential for the production of sperm and eggs in animals like mice and fish, but this is the first time that scientists have proved that they lead to sperm cells with little mobility, and are thus a factor in human fertility.
Mutations in the Piwi gene do not affect female fertility, but women with the mutation have a 50 percent chance of transmitting the gene to their children, potentially rendering their sons infertile. In the future, gene testing will be able to show whether men are infertile and whether women are carriers of the mutation. Liu and her team have applied for a patent for these tests.
During the course of their research, Liu’s group also discovered a possible treatment for infertility. A certain peptide — a combination of amino acids — can “rescue” sperm affected by human Piwi mutations. After the peptide was introduced in mice with the gene mutation, researchers found that the animals’ sperm recovered its motility.
But according to Liu, the peptide cannot be applied to humans, and her team is currently searching for chemicals that serve the same function. “It will take some time for us to find the suitable small-molecule chemicals,” Liu said. “But the future is promising.”
Editor: Kevin Schoenmakers.
(Header image: Science Photo Library/VCG)