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THURSDAY, April 8 (HealthDayNews) -- Swedish scientists have found two genes directly linked with increasing the risk of asthma and other breathing problems, a discovery that may open new avenues to drug therapy.

Though it is not the first study to find a genetic association to asthma, it is the largest to date -- almost 900 people were looked at -- and experts say the link is the strongest yet.

Theses genes, called GPRA and AAA1, are located on chromosome 7. Mutations in chromosome 7 have been linked to asthma, and parts of the GPRA gene have been associated with asthma and certain inherited allergies.

"These genes on chromosome 7 are genetic risk genes for developing asthma," said lead researcher Dr. Juha Kere, a professor of molecular genetics at the Karolinska Institute in Stockholm.

Kere and his colleagues studied these genes in biopsy samples from three different populations, two in Finland and one in French Canada. In addition, they tested the function of the genes in mice, according to their report in the April 9 issue of the journal Science.

These genes make a protein that is found on the cells of the airway and also on smooth muscle cells, Kere said. Both are important cell types in asthma, he added.

Since asthma is an inflammation coupled with a muscle constriction of the airway, these genes appear to play a direct role in the disease, Kere said.

Kere added that not only are these proteins involved in asthma, but they also are drug targets for treating asthma.

"More than half of the asthma medications sold today are targeted at these proteins," Kere said. "That makes these new genes promising targets for developing new drugs for asthma."

Unlike other genes that have been identified as playing a part in asthma, these new genes appear to be more common risk genes than many of the others, Kere said.

In fact, the altered form of the gene linked to asthma is found in almost half of the asthma patients the researchers studied, he said. How these genes affect other asthma sufferers is not clear, Kere added.

However, Kere believes that this same genetic pathway might be altered in other ways in most asthmatics, although this still needs to be investigated.

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.

The problem is working out how these genes interact to cause the inflammation and changes in the lungs that results in asthma, he added.

However, if the genes highlighted in this study identify pathways that are important in lung function or in inflammation, then it could lead to developing new drugs to treat asthma, Rosenwasser said.

More information

The American Academy of Allergy, Asthma and Immunology and the National Institute of Allergy and Infectious Diseases can tell you more about asthma.

(SOURCES: Juha Kere, M.D., Ph.D., professor of molecular genetics, Karolinska Institute, Stockholm, Sweden; Lanny J. Rosenwasser, M.D., professor of allergy and immunology, National Jewish Medical and Research Center, and professor of medicine and immunology, University of Colorado Health Science Center, and past president, American Academy of Allergy, Asthma and Immunology, Denver; April 9, 2004, Science)

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