Researchers from the University of Social Welfare and Rehabilitation Sciences in Tehran, Iran, have stumbled upon two heritable mutations that lead to infertility in men. The finding, published last week in the American Journal of Human Genetics, has opened up a promising avenue of research for the field of male contraception.
Whilst screening a cohort of Iranian men for genes implicated in deafness, scientists noticed two mutations in the CATSPER1 gene - in two different families. Subsequent experiments confirmed that carriers of the genetic changes were infertile. Both mutations are thought to cause either a very truncated (and therefore defective) version of the protein, or no protein at all. The mutation was absent in 576 unaffected individuals.
CATSPER1 encodes one of a family of four proteins found in the tails of mammalian sperm cells. The four work together to form a calcium ion channel, thought to be essential for the exaggerated motility observed during the final stages of a sperm cell's movement through the oviduct. Previous research on mice - carried out at Harvard University, US - highlighted the importance of this ion channel for fertility. Yet this is the first occasion that mutations have been discovered in humans.
Dr Michael Hildebrand of the University of Iowa, US, and leader of the study, said: 'Identification of targets such as the CATSPER1 gene that are involved in the fertility process and are specific for sperm - potentially minimizing side effects of a drug targeting the protein's function - provide new targets for a pharmacological male contraceptive'. A technique known as immunocontraception, still in its infancy, has been considered, whereby an antibody is designed to bind and block a target protein.
'Now that women have such a great range of contraceptives to choose from, it is vital that men have options too,' said a spokesperson for the FPA, formerly the Family Planning Association. 'Although more research must be done to make sure any male contraceptive is safe and effective, it is great that efforts are being made to increase contraceptive choice'.