Largest UK study finds genetic origin of common diseases

The Wellcome Trust Control Consortium, a collaboration of 200 UK scientists from 50 leading research groups at various UK institutions, funded a 9 billion pound study, the largest of its kind till date, wherein they analyzed the genetic origin of common diseases such as diabetes, rheumatoid arthritis and coronary heart disease which was published on June 7, 2007 in the journals, Nature and Nature Genetics.

Under the study, the researchers examined DNA samples from 17000 people i.e. nearly 10 billion pieces of genetic information across UK for 2 years. The DNA samples were of 2000 patients for each disease analyzed and 3000 control samples. The seven diseases studied for identifying common genetic variations were bipolar disorder, Crohn's disease (a type of inflammatory bowel disease), coronary heart disease, hypertension, rheumatoid arthritis and type 1 and type 2 diabetes.

The scientists discovered over 20 genes and regions of the human genome that are believed to play a role in the growth of such diseases but were not previously thought to be related to the disease.

A very significant finding of the study was the discovery of four chromosome regions containing genes that developed type 1 diabetes and three new genes that developed the Crohn’s disease. A gene that linked these two diseases called PTPN2 was also discovered.

Many genes affecting the growth of bipolar disorder and a genetic region that increased a person's risk of coronary artery disease by almost 50 percent was discovered.

"The link between type 1 diabetes and Crohn's disease is one of the most exciting findings to come out of the Consortium. 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 disease (Autophagy) may give us clues on how to treat type 1 diabetes in the future ", said Professor John Todd from the University of Cambridge who supervised this part of the study.

The Director of the Wellcome Trust, Dr. Mark Walport was also surprised with the results and confirmed that the scientists examined half a million SNPs and found more than 10 genes plus fragments of DNA that apparently increased the risk of some common diseases in the study.

"This research shows that it is possible to analyze human variation in health and disease on an enormous scale. It shows the importance of studies such as the 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.", he added.

Lead researcher Peter Donnelly of the Department of Statistics at the University of Oxford in England and Chairman of the Wellcome Trust Case Control Consortium said, "These are like heart disease, schizophrenia, depression and arthritis, where we have known that genetics plays a role, but we haven't been able to pinpoint the genetic factors which are involved. Our study is a new dawn to understanding genetic components of common diseases”.

He also said that despite the various researches conducted worldwide to find out the causes of such diseases, not much success has been found till date and this new study seems promising enough to reveal the biological factors dominating their occurrence which may even help in advancement of personalized treatments as people at high risk of catching these diseases may be spotted in time. It may also help to devise new treatments for such diseases that target their causes.

Further studies with a larger sample will be conducted to confirm the results and extensive research to discover genetic components of tuberculosis, breast cancer, autoimmune thyroid disease, multiple sclerosis and ankylosing spondylitis, a rheumatic disease of the spine will also be held.

The human genome is composed of 24 distinct chromosomes with a total of approximately 3 billion DNA base pairs containing an estimated 20,000–25,000 genes of four DNA building blocks with the chemical names adenine (A), thymine (T), guanine (G) and cytosine (C).

Most studies of human genetic variation have focused on single nucleotide polymorphisms (SNPs), which are substitutions in individual bases along a chromosome. It has been estimated that SNPs occur on average somewhere between every 1 in 100 and 1 in 1,000 base pairs in the euchromatic human genome, although they do not occur at a uniform density.

UK Biobank is a proposed large long-term study in the United Kingdom (UK) intended to investigate the respective contributions of genetic predisposition and environmental exposure (including nutrition, lifestyle, medications etc.) to the development of disease. It is scheduled to begin in 2007 and is funded by the UK Department of Health, the Medical Research Council, the Scottish Executive, and the Wellcome Trust medical research charity. The amount needed is 61 million GBP.

The study will follow about 500,000 volunteers in the UK aged 40-69. Initial enrollment will take place over a number of years with the volunteers being followed for 25 years thereafter.