A new discovery that plays an important role in sperm development may shed light on male infertility. Scientists at the Howard Hughes Medical Institute believe they have discovered that defects in the human gene may contribute to certain male infertility conditions.
Howard Hughes' team found that mice lacking the human gene were infertile and produced only a few abnormal sperm. One of the UK's leading male fertility experts says he hopes the findings will provide some answers to why some men are unable to have children. Many of the causes of "low fertility" in men remain obscure and not fully understood.
Abnormally shaped sperm or very low sperm counts are two reasons why some men are unable to have children. Many studies are looking for the genetic defects that cause these diseases. Howard Hughes' team of experts believe that the human gene is essential for "sperm formation", which allows the DNA needed to make an embryo to condense into a tight ball at the sperm head so that it can damage the outer surface of the sperm through the egg. Spermatogenesis is the final stage of sperm maturation, when cells form pseudopodia, acquire the ability to crawl and are able to fertilize an oocyte.
To determine whether the human gene affects sperm production, they experimented with mice and bred the animals without the human gene. It turned out that these mice had abnormally small testes, produced very low numbers of sperm, and were unable to produce offspring. They even found that not only were the testes abnormally small, but the few sperm they produced had abnormally shaped heads and tails that turned out to be immobile. When the sperm was examined under a microscope using staining techniques, it was found that the DNA in the sperm head was not packaged properly.
"Deficiencies in this gene may be responsible for some male infertility," said Dr. Zhang Yi, project leader of the Howard Hughes team. "Because this gene has a very specific effect on the development of functional sperm, it has great potential as a target for new infertility treatments that are less likely to interfere with other functions of the body," he said.
Although the importance of the human gene has been demonstrated in mice, it is uncertain whether it has the same effect in humans. The next big step for the team is to look at the DNA of infertile men to see if any of them are missing it.
According to Dr Alan Pesci, Lecturer in Andrology at the University of Sheffield and Secretary of the British Fertility Society, little is known about the genes that control sperm development. "The way sperm DNA is packaged into the sperm, and we know very little about it. Extrapolate this study to human males to see if it can explain why some men don't produce healthy sperm and are therefore infertile. It will be very useful," he said.
The way the DNA of sperm is connected to the sperm head is very distinctive, and we recognize very little about that. He similarly said that it would be very beneficial to translate this examination to guys and notice if it can provide an explanation for why a few men do not produce wholesome sperm, so they are not fertile.
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