Infertility and Sperm With No Mask

Male infertility may be caused by missing the protein DEFB126

(RxWiki News) Around 15 percent of couples in the United States have difficulty conceiving. Since half of infertility issues can be attributed to males, researchers are focused on finding a potential missing link.

A recent international study identified a protein called DEFB126 that is supposed to encapsulate sperm to allow evasion from a woman's immune system and survive the uterine environment until fertilization. When a man has two defective copies of the gene responsible for producing it, fertility is greatly reduced.

"Ask the fertility expert to test sperm motility in mucus."

Gary Cherr, Ph.D. a professor at the UC Davis Bodega Marine Laboratory and Center for Health and Environment and senior author of this paper reports that as many as 25 percent of men worldwide carry two copies of the defective gene for the protein DEFB126. 

Ted Tollner, Ph.D., first author of the paper and adjunct assistant professor in the UC Davis Department of Obstetrics and Gynecology reports that one of the many mysteries surrounding human fertility is that sperm quantity and quality don't necessarily impact a man's fertility. According to Cherr, 70 percent of men experiencing fertility problems don't have sperm quality or quantity issues. Their sperm function properly, but without the protein coating are unable to penetrate mucus and reach the egg.

The research team hopes that a test can be developed to diagnose men with the protein defect. This then could expedite fertility treatment by sending couples identified by the test directly to intracytoplasmic sperm injection (ICSI) and avoid other costly fertility workups.

Sperm from men with the defective DEFB126 genes look normal and swim normally under a microscope. However, when an artificial gel created to mimic human cervical mucus was introduced, they were not able to swim efficiently. The research team found that when the DEFB126 was added to the sperm, they recovered their effective swimming abilities.

Scott Venners, Ph.D., M.P.H.. an assistant professor of epidemiology at the health sciences at Simon Fraser University in Barnaby, British Columbia, Canada reported via a teleconference call that once the research team discovered the DEFB126, they followed 500 couples for 22 months who were trying to conceive their first child in China, a population known to have high infertility rates. The males genotypes were established. Those who had two copies of the genetic mutation had a 30 percent less likelihood of giving birth to a child than the population without two copies.

A paper covering this work is published in the journal Science Translational Medicine.

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Review Date: 
July 19, 2011