Sperm's genetic fingerprint

A team of researchers based at universities in Detroit, US, and Leeds in the UK, have identified the genetic pattern of healthy sperm. They believe the discovery could be a major step forward in our understanding of male infertility and perhaps lead to the development of new male contraceptives. Male fertility problems account for half of assisted reproductive techniques. But, for the majority of infertile men, the direct cause of the problem is unknown.

Findings from several previous studies have suggested that sperm cells have a complex genetic code made up of components called mRNA (messenger RNA), the genetic material in cells that translates protein-building instructions from DNA. The researchers analysed millions of sperm cells from fertile men. They compared the mRNA content of one man's sperm to that of two pooled samples - one from 19 men and one from nine fathers. They found 'remarkably little variation between the individual and the pooled sample'.

Reported in the Lancet medical journal, the researchers say that fertile sperm appeared to have a 'mini-genome' of around 3000 individual mRNAs. They say that the 'because there was a high level of correspondence between the pooled and the individual ejaculates, we have identified a set of RNAs that are like a fingerprint for fertility'. They hope that this 'gold standard' can be used in the future as a benchmark for comparisons of genetic analysis from sperm of infertile men.

Chris Barratt, professor of reproductive medicine at Birmingham university in the UK, said that 'it's a significant advance that they've come up with a fingerprint, albeit a first draft, but it's a good first draft'. He predicted that the findings could lead to clinical tests in about two years.