Gene Mutation Affects Sperm's Ability to get Around, Fertility.

Science Editor

Almost 15 percent of couples are infertile, at least by the definition of the World Health Organization: no pregnancy after a year of trying without birth control. In about half of those cases, the male partner is the one who is infertile; and in nearly a fifth of those cases, no one can figure out why.

But a team of researchers has identified a mutation that may explain some of those cases. In an epidemiological study of 500 Chinese families, those couples where the male was homozygous for a mutation in the DEFB126 gene had a 30 percent reduced birth rate over a period of 22 months.

The researchers published their findings in the July 21, 2011, issue of Science Translational Medicine.

The DEFB126 protein …