Childhood asthma gene clue

A new gene variant has been found that leads to an increased risk of children developing asthma. A team at the National Heart and Lung Institute, Imperial College, London performed a 'genome-wide association' study, analysing 317,000 genetic variations  SNPs in 994 patients with childhood onset asthma. The results, published in Nature, point to a clear association with a number of SNPs located on chromosome 17.

A gene within this region, ORMDL3, was consistently associated, with an increase in activity upon the presence of the variant SNPs. The disease SNPs raise the risk of developing the disease by 60 per cent.

Asthma is a chronic condition whereby sufferers periodically experience constriction of the bronchi - airways - leading to 'wheezing' and chest tightening. The extent of constriction and the periodicity of episodes can vary widely, and it can be life threatening.

Despite being one of the fastest growing disorders in the Western population - one in ten children and on in twenty adults have asthma - scientists are still in the dark as to the pathology of the disorder. Current thinking suggests asthma is induced by an interaction of genetic and environmental factors, but what these factors are remain elusive.

To date, 14 genes have been associated with asthma, ten have proven unreliable markers, four have gone on to show strong associations. ORMDL3 has shown the most direct association so far.

ORMDL3 is an ancient gene found in organisms as rudimentary as yeast. It is switched on in the blood and is thought to have links to the immune system. This fact lends credence to the idea that asthma may be a result of an inappropriate immune response against allergens. Despite posing no pathological threat to humans, it is thought that some individuals mount an immune response against benign airborne particles such as dust mite body parts. The inflammation induced by this can lead to the irritation of muscles, which then constrict the airways. The exact biological explanation for this response is still unknown.

Co-author Dr Miriam Moffatt said: 'These novel findings do not explain completely how asthma is caused, but they do provide a further part of the gene-environment jigsaw that makes up the disease'. The findings have potential for both predictive testing and as a new drug target.