Gene defect leads to infertility in men

Common genetic defect responsible for male infertility

22.07.2011

Scientists have discovered a very common genetic defect in men that leads to infertility. The gene variant could be one of the reasons why a high proportion of men suffer from inability to produce or restrict their fertility. In those affected, the sperm can not penetrate to the egg and are most likely intercepted by the female immune system.

A detected gene variant could be the main cause of a variety of male fertility. Because according to recent studies, every sixth couple in Germany without children. In 50 percent of cases, this is due to a man's weakness. According to the latest figures, about 1.5 million German men suffer from fertility. In a fifth of patients, the reason remains unclear because quality and quantity do not indicate fertility. Then in most cases, only artificial insemination will help.

Gene mutation without sacrificing quality and quantity
Physicians are often at a loss because the cause can not be diagnosed on the basis of sperm quality. The first step in the investigation is usually to measure seeds for number, texture, shape and movement. But the number and quality says nothing about the authorship of the problem. „In 70 percent of the patients, the infertility can not be explained by the number and quality of the sperm, "explains Gary Cherr „University of California“ in the US city of Davis. The urologist has conducted a study with researchers to shed more light on the problem. The scientists came up with an amazing connection and were able to solve at least part of the puzzle. Thus, in a large number of men, a genetic defect could be responsible for impaired fertility. Every fifth man suffers from this not uncommon gene variant. This reduces the possibility of sperm cells to fertilize the woman's egg, as the research team in the scientific journal „Science Translational Medicine“ reported. However, there are different mutations.

Defective gene DEFB126
As a gene, the researchers identified the variant named DEFB126, which is an altered protein form of the „Beta-defensin“ is. This protein is produced in the male epididymis and is located on the sperm surface after production. Sperm from volunteers who had the variant DEFB126 could penetrate significantly worse through the uterine mucus, than semen cells of the comparison subjects.
The study was based on an already conducted study with monkey sperm. There, researchers were able to identify defensives that are used primarily to repel microbes. In addition, the protein helps to move through the mucus of the cervix, to escape the female immune system and to attach to the fallopian tube wall. In the lab, the scientists found that a mutation slowed the rate of uterine secretion by 84 percent. But this mutation prevents fertilization of the egg to a considerable extent. Whether such defective sperm are also maltreated by the female immune system is still largely unexplained.

Biennial study with Asian men
A study of 500 otherwise completely healthy Chinese men should now check the gene mutation in humans. All subjects were young and newly married and wished to have children. The researchers accompanied the young couples for a total of two years. It turned out that among the men who had the genetic defect, the probability was 30 percent lower, to father a child. The sperm showed no loss of quality and speed. The results must now be reviewed through more extensive research. After all, the mutation is just as likely to be found in men in the American, Asian, and European continents at a similar rate. As an explanation, the scientists suspect that men with an intact and a defective form are likely to have an advantage. It is also unclear why the defect is not already extinct, if the effects are so serious. Most likely, the researchers say, men who own only part of the gene variant have an advantage over the men who inherited both variants.

Artificial insemination can help
The doctors emphasized that one „artificial insemination help with the desire to have children“ could. After all, only the defective protein prevents penetration into the egg. The quality is not different from others. (Sb)

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Picture credits: Thommy Weiss