Male infertility linked to defective sperm
Scott Venners, SFU Health Sciences, firstname.lastname@example.org, 778.782.8494
Dixon Tam, SFU PAMR, email@example.com, 778.782.8742
Simon Fraser University’s Scott Venners is part of an international team of scientists that has discovered a mutation in a gene that helps explain why some men are less fertile than normal.
The gene encodes a protein called beta defensin 126, which coats the surface of sperm and helps it penetrate cervical mucus in women. Men with a variant of this gene, called DEFB126, lack beta defensin 126, making it much more difficult for sperm to swim through the mucus and eventually join with an egg.
This genetic variation in DEFB126 likely accounts for many unexplained cases of infertility. Screening for variants of DEFB126 in men could improve current testing, which still fails to find the cause of infertility in almost one-fifth of infertile couples.
“Infertility in many countries around the world occurs in 13 to 14 per cent of couples,” says Venners. “In about half of infertile couples, the identified cause of infertility lies with the male partner. However, infertility is still unexplained in about 17 per cent of infertile couples and we think that our finding might explain some of these cases.”
Researchers from SFU, University of California at Davis, University of Illinois at Chicago, and China’s Anhui Medical University collaborated on this project, which included studying 500 newly married Chinese couples.
Scientists found the lack of beta defensin 126 in men with the DEFB126 mutation lowered fertility (even among men who did not display other deficiencies usually associated with infertility, like inadequate sperm count and low sperm motility). Wives of men with the beta defensin 126 variant were significantly less likely to become pregnant compared to other couples, and had a 30 per cent reduced rate of birth.
“The research started with studies in non-human primates at UC Davis where it was established that DEFB126 was important for male reproduction,” Venners explains. “But no one expected to find a common genetic variant in humans that would nullify DEFB126. We predicted this generic variant would lead to reduced fertility in the men who had it, and that is what our research confirmed.
“The next steps are to confirm these findings in another population then move toward methods of clinical diagnosis and treatment of infertility.”
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