Applying a new genomic technique to a large group of patients, researchers in Britain have detected DNA variations that underlie seven common diseases, discovering unexpected links among them.
The variations pinpoint biological pathways underlying each of the diseases, and researchers hope that as the pathways are analyzed, treatments will emerge.
The seven common diseases are bipolar disorder, coronary artery disease, Crohn's disease, hypertension, rheumatoid arthritis, and Type 1 and Type 2 diabetes.
Unveiling the complex genetics of common diseases was the promised payoff of the $3 billion human genome project, completed in 2003, but progress was slow until the recent development of devices that in a single operation can read the DNA sequence at up to 500,000 points across an individual's genome.
With the devices, called chips, researchers can compare large numbers of patients with healthy individuals, looking for points of differences in their genomes that may be associated with disease.
The approach is known as whole genome association, and studies on Type 2 diabetes, heart disease and breast cancer have been reported within the last few weeks. Those and the new study, which was financed by the Wellcome Trust of London, demonstrate the power and reliability of this method.
"It's now absolutely clear that this is a new dawn in the genetics of common human diseases," said Peter Donnelly, an Oxford University statistical geneticist and chairman of the consortium of 50 institutions involved in the study.
The consortium compared 2,000 patients with each disease from across Britain with 3,000 healthy individuals as controls, half of whom were born in a single week in 1958. The consortium's findings are published in today's Nature, along with reports from two groups that largely confirm the consortium's genomic hits in independent patient groups suffering from Crohn's disease and Type 1 diabetes.
The consortium discovered some 24 variants strongly linked to disease, about half of which have been found already by other groups and half of which are new.
Among its most interesting findings is that genetic variants close to a gene known as PTPN2 are associated with both Crohn's disease and Type 1 diabetes. The link may be that both are autoimmune diseases and that the gene helps regulate the immune system. Researchers hope that analysis of the gene's operations may produce a treatment for the two diseases.
The consortium also found a genetic variant on chromosome 7 that carries a high risk of rheumatoid arthritis for women, but none for men. Very few such variants are known in diseases common to both sexes, Donnelly said.
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