Human genes linked to asthma are discovered

Two human genes linked to the development of asthma have been discovered, shedding new light on the rise in the incidence of the disease among children and its treatment.

About 5.1 million people in Britain are treated for asthma and there has been a 50 per cent increase in childhood cases in the past 30 years.

Asthma can stem from a genetic predisposition, but today's paper by Prof Juha Kere, of the Karolinska Institute, Stockholm, confirms that genes alone cannot explain the recent rise, suggesting changes in the environment are responsible.

In Science, Prof Kere reports on how genetic spelling mistakes in the genes GPRA and AAA1 associate strongly with asthma and inherited allergies. These genetic changes were found in as many as one quarter of the populations examined and "very likely the British population too", report

According to asthma is an immunological disease characterized by recurrent breathing problems due to a narrowing of the airways.

The cardinal symptoms of asthma include wheezing, shortness of breath and labored breathing.

Although researchers had previously linked three other genes to asthma, the studies involved a much smaller sample size.

In addition, the studies revealed a relatively weak genetic link to asthma susceptibility. Kere and colleagues found that both healthy and asthmatic people from families with asthma carried one of seven possible variant DNA sequences, known as haplotypes, on chromosome 7.

To make certain these haplotypes weren't unique to Finns, Kere enlisted the help of Thomas Hudson, a haplotype expert at McGill University in Montreal, Quebec, Canada.

Hudson collected nearly 400 DNA samples from asthmatics and non-asthmatics in Quebec and after close inspection determined that people there had the same haplotypes.

From here the researchers narrowed the search to two genes thought to be strongly linked to asthma susceptibility.

In addition, how alterations in these genes work to cause asthma is not known. The researchers' next task is to uncover how these genes work and how they are related to other genes involved in asthma, Kere said.

Dr. Lanny J. Rosenwasser, an immunology and asthma expert at the National Jewish Medical and Research Center in Denver, said that this is a solid and important finding.

"But asthma is such a complex genetic disease that there are probably dozens of these kinds of findings that have been made and will continue to be made as we try to piece together how the pathogenesis of asthma works," he said.

"This study highlights a potential contributor to asthma that we didn't know much about before," he added.

There is clearly an important genetic component to asthma, but - like other diseases - one set of genes is not the major cause. There may be as many as 50 genes, with many mutations of each that contribute to asthma, Rosenwasser said, inform

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