Canadian scientists have identified a mouse gene involved in sperm development, which they say could help research into human male infertility and into contraception. The researchers, based at the University of Toronto, found that mice lacking the Fkbp6 gene had no spermatids, the cells that grow into sperm. The team, who were originally investigating possible links between the gene and heart disease, published their findings in the journal Science. 'That this gene would control male fertility was completely unexpected' said lead researcher Josef Penninger.

The Fkbp6 gene appears to be essential for normal sperm development in mice, but has no effect on egg cells in female mice. Male mice bred to have the gene missing had much smaller testes than normal and produced no sperm cells, but they had normal levels of sex hormones. 'So it's possible that Fkbp6 might be perfect for the development of a male birth control pill' speculated Penninger. Alterations in the human version of the gene might also explain some cases of male infertility, say the researchers.

Also reported last week was the development of a new method for sorting live sperm from dead or immobile ones. Researchers at the University of Michigan in Ann Arbour have created a stamp-sized silicon chip, etched with lanes less than half a millimetre wide. When a sperm sample is dripped into one end of the chip and salt water into the other, the two lanes merge and healthy sperm swim into the water, leaving the dead sperm behind. A sample with only 45 per cent healthy sperm came out of the chip with this figure increased to 98 per cent. The scientists, who published details of their device in Reproductive Biomedicine Online, next have to show that the purified sperm can fertilise eggs.