A study has shown that mutations in the NR5A1 gene may be responsible for many unexplained cases of male infertility.

The research team, led by scientists from the Pasteur Institute in Paris and Institute of Child Health in London, screened a group of 315 men who were unable to producesperm, for mutations in the gene NR5A1.

The gene encodes for a protein that has a critical role in the development of the reproductive organs and in reproduction, and has previously been linked to problems with sexual development in both men and women.

The researchers found that seven of the effected individuals had mutations in this gene, while no mutations were found in a control group of 729 men who had normal sperm production.

Four of these men were also found to have altered levels of sex hormones, and another had testicular abnormalities, suggesting a link between the mutations and the problems with sperm production.

The study, published in the American Journal of Human Genetics, represents an important step in the search for genes that may be responsible for male infertility, which accounts for 30 to 50 percent of the fertility problems faced by couples trying to conceive.

The authors told the BBC: 'Approximately four percent of men with otherwise unexplained failure to produce sperm carry mutations in the NR5A1 gene'.

To date only a small number of genes have been linked to male infertility, with the majority of sperm production problems having no obvious cause.

Dr Allan Pacey, a fertility expert from Sheffield University said: 'Although this gene defectaffects only a small number of men, we need more studies like this so we can fill in the gaps in our knowledge and possibly one day build a robust diagnostic test for male fertility based on genetics'.

Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.