A HUGE advance in understanding the genetics behind some of the world’s most common diseases has been revealed by scientists in the United Kingdom.

　　The landmark Wellcome Trust study analysed DNA from the blood of 17,000 people to find genetic differences. Its researchers found new genetic variants for depression, Crohn’s disease, coronary heart disease, hypertension, rheumatoid arthritis and type 1 and 2 diabetes.

　　The findings have been described as a new chapter in medical science. It is hoped they will pave the way for research into new treatments and genetic tests.

　　The study should help researchers to understand better how disease occurs, what people are likely to get ill, and to fight such illnesses with better treatments.

　　Funded by nine million pounds, the Wellcome Trust Case Control Consortium involved 50 leading research groups analysing the DNA (deoxyribonucleic acid) from 2,000 patients for each of the seven conditions and 3,000 healthy volunteers.

　　“Many of the most common diseases are very complex, part ‘nature’ and ‘nurture’, with genes interacting with our environment and lifestyles,” said Professor Peter Donnelly, chair of the consortium, and who is based at the University of Oxford.

　　“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.”

　　The study has substantially increased the number of genes known to play a role in the development of some of our most common diseases. Many of these genes that have been found are in areas of the genome not previously thought to have been related to the diseases.

　　“Just a few years ago it would have been thought wildly optimistic that it would be possible in the near future to study a thousand genetic variants in each of a thousand people,” said Dr Mark Walport, director of the Wellcome Trust, the UK’s largest medical research charity that funded the study.

　　“What has been achieved in this research is the analysis of half a million genetic variants in each of 17,000 individuals, with the discovery of more than 10 genes that predispose to common diseases.

　　“This research shows that it is possible to analyse human variation in health and disease on an enormous scale. It shows the importance of studies such as UK Biobank, which is seeking half a million volunteers aged between 40 and 69, with the aim of understanding the links between health, the environment and genetic variation. New preventive strategies and new treatments depend on a detailed understanding of the genetic, behavioural and environmental factors that conspire to cause disease.”

　　Among the most significant findings are four chromosome regions containing genes that can predispose to type 1 diabetes and three new genes for Crohn’s disease (a type of inflammatory bowel disease). For the first time, the researchers have found a gene linking these two auto-immune diseases, known as PTPN2.

　　The study has also confirmed the importance of a process known as autophagy in the development of Crohn’s disease. Autophagy, or “self-eating”, is responsible for clearing unwanted material, such as bacteria, from within cells. This may be key to the interaction of gut bacteria in health and in inflammatory bowel disease, and could have clinical significance in the future.

　　“The link between type 1 diabetes and Crohn’s disease is one of the most exciting findings to come out of the consortium,” said Professor John Todd from Cambridge University, who led the study into type 1 diabetes. “It is a promising avenue for us to understand how the two diseases occur. The pathways that lead to Crohn’s disease are increasingly well understood and we hope that progress in treating Crohn’s may give us clues on how to treat type 1 diabetes in the future.”

　　Research from the consortium has already played a main part in identifying the clearest genetic link yet to obesity and three new genes linked to type 2 diabetes, published in April in advance of the main study. It has found independently a major gene region on chromosome 9, identified by independent studies on coronary heart disease.

　　Researchers analysed DNA samples taken from people in the UK - 2,000 patients for each disease and 3,000 control samples - to identify common genetic variations for seven major diseases. These are bipolar disorder, Crohn’s disease, coronary heart disease, hypertension, rheumatoid arthritis, and type 1 and type 2 diabetes. For each disease, the researchers will study larger population samples to confirm their results.

　　Although the human genome is made up of more than three billion sub-units of DNA, called nucleotides (or bases), most of these show little in the way of differences between individuals. A substantial part of the variation in DNA sequence between individuals is due to single nucleotide polymorphisms (differences), also known as SNPs.

　　There are about eight million common SNPs in European populations. Fortunately, because SNPs that lie close together on chromosomes often tell quite similar stories, researchers in the consortium were able to explore this variation through analysing a subset of these SNPs (about 500,000).

　　Professor Donnelly added: “Human genetics has a chequered history of irreproducible results, but this landmark collaboration of scientists in Britain has shown conclusively that the new approach of analysing a large subset of genetic variants in large samples of patients and healthy individuals works.

　　“We are now able to effectively scan most of the common variation in the human genome to look for variants associated with diseases. This approach will undoubtedly herald major advances in how we understand and tackle disease in the future.”

　　Further analysis as part of the Wellcome Trust Case Control Consortium will be looking at tuberculosis, breast cancer, auto-immune thyroid disease, multiple sclerosis and ankylosing spondylitis. The results are expected later this year.　　 (Source: British Consulate-General in Chongqing)