23 July 2012

Appeared in BioNews 666

Results of the first study to sequence the genomes of individual sperm cells obtained from one person have revealed significant genetic differences between them, confirming the belief that each sperm is unique. It is hoped the technique could be applied in fertility treatments to identify genetic mutations that may occur in the recombination process.

'For the first time we were able to generate an individual recombination map and mutation rate for each of several sperm from one person', said Professor Barry Behr from Stanford University in California, USA, who was involved in the study. 'Now we can look at a particular individual, make some calls about what they would likely contribute genetically to an embryo, and perhaps even diagnose or detect potential problems'.

The team overcame significant technical obstacles to sequence each individual sperm cell, and by using a novel technique the researchers managed to separate 91 sperm cells and amplify their DNA for sequencing.

The results showed that recombination - a naturally occurring process whereby chromosomes in the sperm are shuffled around during meiosis - was observed in unexpected places, suggesting this shuffling process is unique in each cell. The findings could explain why siblings have significant genetic differences between them, confirming the recombination process as being partly responsible for genetic diversity.

Whereas previous studies have only looked at recombination across populations, this was the first study to observe the process in individuals. The team now hopes its findings can be applied to fertility treatments, with some commentators saying the technique could also be used to study cancer.

Study leader Stephen Quake, professor of bioengineering at Stanford University, said: 'People have difficulty conceiving children due to reproductive disorders, and this will provide a very effective way to analyse when there are problems with their sperm'.

Jianbin Wang, a member of Professor Quake's team, explained the technique could also be used to select eggs for IVF. 'We can use those cells to analyse an egg's genome, and screen for genetic diseases', he said. This would be an improvement on existing, more difficult techniques, explained the New Scientist. 'Our technique may make the process easier', said Wang.

The research was published in the journal Cell.