Genetic clue may bring male Pill

Attempts to come up with an oral contraceptive for men have so far failed because of the immense numbers of sperm produced each day as part of normal male reproduction.

The fault occurs in a gene that should enable the sperm to wriggle through the outer membrane of an unfertilised egg.

Scientists hope that by studying the way the gene works they might be able to overcome infertility in some men as well as design a drug that causes a reversible change in the ability of the sperm to fertilise an egg.

Michael Hildebrand of the University of Iowa said that studies of extended families in Iran have identified a gene, CATSPER1, involved in an hereditary form of infertility. Further studies on mice showed the gene to be responsible for controlling the vigorous movements of sperm as they approach and penetrate the unfertilised egg.

The study, published in The American Journal of Human Genetics, provides fresh insight into ways of developing drugs that could interfere with the fertilising ability of sperm, Dr Hildebrand said.