Green sperm cast light on male infertility

Scientists at Oxford University have used a jellyfish gene that codes for a green protein to 'light up' hamster sperm and enable them to study the function of fertility genes. Dr John Parrington, who leads the research team, said that the real aim of the study 'is to use this technique to study the function of genes that are important during fertilisation and that may cause infertility if they become defective'.

Many cells of the body can be cultured and genetically modified in the lab, but sperm cells can be particularly problematic due to their small size, unusual shape and short survival period outside the body. The Oxford team has developed a new technique which will enable them to investigate sperm much more effectively. The team injected a jellyfish gene into hamster testes. The introduction of this new gene causes the sperm mitochondria - the 'power houses' of the cell - to shine green under fluorescent light. The scientists plan to use the new technique to focus on the mechanism by which sperm entering an egg trigger it to develop into an embryo.

The technique may also help scientists develop new ways of creating genetically modified animals for other research. Currently, modified animals are created using the relatively inefficient transgene method, where synthetic genes are introduced into an egg. Attempts to use this transgenic method have so far failed in important model species such as hamsters and guinea pigs. Creating animals using the newly developed method - modifying the sperm and then fertilising a normal egg with it - could potentially reduce the number of mice used in medical research and allow scientists to use species that are better models for human disease.

Dr Allan Pacey, secretary of the British Fertility Society, described the research as an exciting development. 'This will allow scientists to examine many aspects of sperm function that would previously have been impossible. There is awful lot to discover about how sperm work and why sometimes they fail to function properly', he said.