Gene findings: Disease-by-disease

A team of UK researchers have identified several genes and regions of the genome involved in seven common diseases - but what are the implications for people suffering from the conditions?

Bipolar disorder

The first genome-wide study of bipolar disorder has shown that there are many genes that influence an individual's susceptibility to the condition and that each gene on its own makes a relatively small contribution to risk. Several of the genes identified are involved in how nerve cells in the brain talk to each other.

Bipolar mood disorders affect around 100 million people worldwide.

Professor Nick Craddock, professor of psychiatry, at the University of Cardiff said: "By helping to unravel the mechanisms of illness, the findings will help pave the way to better diagnosis and treatment. Some new therapies based on a better understanding of the illness will involve novel drugs but others are likely to include forms of education, lifestyle advice and talking treatments."

Coronary heart disease

Various genetic regions that increase the risk of coronary artery disease have been found. One region on chromosome 9, increases the risk by almost 50% in people with one copy of the variant, and almost doubles the risk in people who carry both copies. Two other studies recently reported the same finding. Heart disease is the UK's biggest killer.

Professor Nilesh Samani, head of cardiovascular sciences at the University of Leicester, said: "Identifying these new genetic variants is a first step that can help us to better predict who are at higher risk, to identify more specific ways of prevention by understanding how these genes operate and potentially, and most excitingly, in developing new treatments."

Crohn's disease

Three new genes increasing a person's susceptibility to Crohn's disease and a region containing several genes were identified in the study. One gene, involved in regulation of the immune system, is shared with type 1 diabetes - the first genetic link between the two diseases. A process known as autophagy - a process of clearing bacteria from within cells - was found to be associated with the development of the disease, which affects up to 60,000 people in the UK.

Dr Miles Parkes, consultant gastroenterologist at Addenbrooke's Hospital and the University of Cambridge said: "The study has substantially advanced our understanding of what causes Crohn's disease. There is a lot of follow-up work required to fully understand the impact of the genetic associations that we have identified. However they have already provided some major leads regarding possible new treatment options."

Hypertension

Hypertension was found to be due to numerous interacting factors rather than any major genetic influence but several genetic markers are being studied further. High blood pressure affects over 16 million people in the UK

Professor Mark Caulfield, Barts and The London School of Medicine, Queen Mary's University, London said: "Our study has highlighted the complex nature of the disease, with few clear cut genes emerging at this stage. "This is probably in part because of the high number of genes involved, which helps to explain why patients with hypertension need to be treated with a combination of multiple drugs."

Rheumatoid arthritis

Several genes have been implicated in rheumatoid arthritis for the first time. Further work will be needed to understand how the variation within these key genes influences the development of the condition, the course of the disease and response to treatment. Around 387,000 people in the UK have rheumatoid arthritis.

Professor Jane Worthington, professor of chronic disease genetics at the University of Manchester said: "Greater understanding of the genetic basis of susceptibility is important to the development of novel therapies particularly those aimed at arresting the disease process before significant disability has occurred."

Type 1 diabetes

Four new chromosome regions and two further possible regions that increase the risk of developing type 1 diabetes - one of which is shared with Crohn's disease. Around five million people worldwide have type 1 diabetes, including over 250,000 in the UK.

Professor John Todd, professor of Medical Genetics at the University of Cambridge: "We now have confirmation that there are at least ten genes or chromosome regions that increase the chances of developing type 1 diabetes. The pathways that lead to Crohn's disease are increasingly well understood. We hope that progress in treating Crohn's disease will give us clues on how to treat type 1 diabetes."

Type 2 diabetes

Data from the project led to the discovery of several novel genes involved in the development of type 2 diabetes and obesity.

One of these genes influences risk of diabetes through an effect on weight and risk of obesity and others have a direct effect on diabetes risk. Around 1.8 million people in the UK have type 2 diabetes

Professor Mark McCarthy, professor of diabetic medicine at the University of Oxford, said: "This research helps us to understand that, for most people at least, an individual's risk of developing diabetes as they get older is influenced by a number of genes, as well as by their environment. Clearly, the more 'high risk' alleles a person inherits, the higher the likelihood that they will go on to develop diabetes."