Second-generation human genome map to shed new light on disease

The International HapMap Consortium, a public-private effort to identify and catalogue genetic similarities and differences in humans, this month unveiled its second-generation version of the human genome; a map three times more detailed than the original version released in 2005. The new map will help scientists to unpick the complex gene-environment interactions that have over time shaped the human genome, helping them to better detect genetic variants involved in common diseases, wrote the consortium in two papers published in the journal Nature.

'Thanks to this consortium's pioneering efforts to map human genetic variation, we are already seeing a windfall of results that are shedding new light on the complex genetics of common diseases', said National Human Genome Research Institute (NHGRI) director Francis Collins, who led the US arm of the study.

If the Human Genome Project aimed to identify the proportion of genetic variation that all humans have in common - now estimated at around 99.5 per cent - then the HapMap consortium may be thought of as a project to understand how the remaining 0.5 per cent makes all humans different from each other. With 3.1 million SNPs (single nucleotide polymorphisms) - single letter changes in the human genome sequence which can act as signposts for genes - mapped out on the second-generation HapMap, the consortium anticipate that the new map will enable researchers to focus their hunt for disease genes to a much smaller area of the human genome, vastly increasing their chances of uncovering new gene variants involved in disease.

It is also widely anticipated that the HapMap may help scientists to begin unlocking some of the secrets of human evolution. Pardis Sabeti, a biologist at the Broad Institute, is interested in using the HapMap findings to fight the disease malaria.

'You can see what are the beneficial tricks that have spread through the human population', said Sabeti, who is co-first author for one of the HapMap reports in an accompanying paper in Nature. 'Finding out which specific mutations are the ones that protect [against disease] will help you think about therapeutics as well'.

To create the second-generation HapMap the consortium analysed the entire genomes of 270 volunteers from all over the globe, comprising Yoruba in Ibadan, Nigeria, Japanese in Tokyo, Han Chinese in Bejing and Utah residents of European descent. The group already have plans to add further DNA samples from people of Kenyan, Tuscan, Indian, Chinese, Mexican and African descent, leading to an even greater understanding of the human genetic variation that makes virtually every human being on the planet unique.