Genetic variants that cause asthma identified

An international study has discovered several genetic variants that substantially increase susceptibility to asthma.

The study, which was co-ordinated by researchers from Imperial College London, was performed by the Gabriel consortium, a collaboration of 164 scientists from 19 countries in Europe, along with other groups in the UK, Canada and Australia. It analysed DNA samples from 10,000 children and adults with asthma and 16,000 non-asthmatics.

The researchers performed more than half a million genetic tests on each subject, covering all the genes in the human genome. The study pinpointed seven locations on the genome where differences in the genetic code were associated with asthma.

The new variants linked to asthma were found in more than a third of children with asthma in the study. The gene with the strongest effect on children did not affect adults, and adult-onset asthma was more weakly linked to other genetic differences, suggesting that it may differ biologically from childhood-onset asthma.

Childhood asthma, which affects boys more than girls and can persist throughout life, is often linked to allergies, and it has been assumed that these can trigger the condition. However, the study found that genes controlling the levels of antibodies that cause allergies had little effect on the presence of asthma, suggesting that allergies are more likely to be a consequence of asthma than a cause.

Some of the genes identified are involved in signaling pathways that tell the immune system when the lining of the airways has been damaged. Other genes appear to control how quickly the airways heal after they have been injured. Identifying these genes should help direct research into new treatments for asthma, the researchers suggest.

The study also found that the genes associated with asthma did not have strong enough effects to be useful for predicting early in life which children might eventually develop the disease. This indicates that environmental factors are also very important in causing asthma to develop. The Gabriel consortium is working to identify environmental exposures that could protect against the illness.

The findings have been published in the New England Journal of Medicine.