London - Pioneering genetic research promises a breakthrough in treating male infertility.
One in six couples fail to conceive after a year of trying, with the man thought to be the cause in half of all cases.
Only a quarter of these problems can currently be explained, but a study has now uncovered 22 potential genetic causes.
Researchers say the discovery will help to develop better diagnostic tests for male infertility.
A team from Radboud University Medical Centre in the Netherlands studied DNA from 108 infertile men and from their parents. The gene sequencing study is the first to investigate the role of "de novo mutations" – genetic mutations that arise in an individual that have not been passed down by the parents.
PhD student Manon Oud said: "These mutations are found in every individual and are part of the normal evolution of the genome. Mostly they do not affect our health. But in some cases they have a strong effect on gene function.
"Until now, their role in male infertility had not been studied." The study was launched at a European Society of Human Genetics conference in Sweden.