Genetic clues to seven diseases uncovered

A team of UK scientists has published details of genetic variations associated with an increased risk of seven common illnesses. The Wellcome Trust Case Control Consortium (WTCCC) has confirmed several previously reported genetic influences on disease, as well as identifying ten new variants. The research, reported in the journal Nature, will help shed light on the causes of bipolar disorder, coronary artery disease, Crohn's disease, rheumatoid arthritis, type 1 diabetes, type 2 diabetes and high blood pressure.

The project, carried out by over 50 different collaborating groups, is the most ambitious 'genome wide association' (GWA) study carried out to date. Such research involves comparing a type of genetic variant called SNPs, in DNA samples from thousands of patients (cases) and unaffected people (controls). In this way, GWA studies aim to identify variants that may have a very subtle effect on the overall risk for conditions such as diabetes - which are thought to be triggered by several different genetic and non-genetic factors.

The WTCCC study looked at 500,000 SNPs in 2000 patient affected by each of the seven disorders, plus a shared group of 3000 unaffected controls - a total of 17,000 people. About half of the variants they pinpointed confirmed findings reported by other groups, for example those implicated in type 1 and 2 diabetes, Crohns disease and rheumatoid arthritis. The other genetic variations were new, with each conferring an average increased risk of between 20-50 per cent (1.2-1.5 times). This, the authors suggest, is not enough to warrant routine genetic testing to identify 'at-risk' individuals.

According to Peter Donnelly, chair of the WTCCC, the new study is 'just scratching the surface', adding 'over the next couple of years, as these sorts of studies are extended, our understanding of the genetics of common diseases will changes enormously'. He also commented that the research was a 'new dawn' and that scientists had learnt more in the past 12 months than they had in 15 years. 'By identifying the genes underlying these conditions, our study should enable scientists to understand better how disease occurs, which people are most at risk and, in time, to produce more effective, more personalised treatments', he said.