More than one couple in 10 in the United States struggles to conceive a child, and the cause of their infertility is often unknown. In July University of California, Davis, reproductive biologist Gary Cherr and colleagues reported that they had identified a surprisingly common genetic mutation that may underlie many unexplained cases of male infertility and offer new avenues for treatment.
The mutated gene, called DEFB126, normally encodes a protein that coats sperm cells and helps them slip through cervical mucus to reach the uterus and the egg within it. Without that protein, the sperm often get stuck. After discovering the mutation, Cherr searched for it in European and Asian men and found that about 20 percent of them have two nonfunctional copies of the gene, so they cannot produce the protein.
Cherr hopes the discovery of the DEFB126 mutation will lead to a genetic fertility test. If an infertile man learns that he lacks the protein, he and his partner can immediately skip to treatments such as in vitro fertilization that do not require sperm to swim through cervical mucus, bypassing unnecessary testing and interventions for both partners. Better yet, research by Cherr’s group in nonhuman primates suggests that it may be possible to simply add the missing protein to sperm when it is needed. “The best-case scenario would be an at-home kit with a foam or vaginal gel,” Cherr says. “That’s our vision, and I don’t think it’s far off.”
Study author Theodore Tollner describes how the beta defensin DEFB126 protein is applied to the sperm surface, and discusses its role in sperm transport in the female reproductive tract.
[Video created by Theodore L. Tollner, 2011; © Science/AAAS]