Asthma-associated SNP May Offer Clues to the Disease and its Treatment

hutterite2.jpgHutterite girl tests lung function

For people with asthma, chronic inflammation in the lungs narrows airways and makes it difficult to breathe.

New research published online this week in the New England Journal of Medicine has found that a version of a SNP in a gene called CHI3L1 can increase a person’s risk of developing the disease.

The CHI3L1 gene encodes a protein called YKL-40 that helps the immune system respond to things like dust mites, cockroaches, fungi, and parasitic worms by triggering inflammation, a central component of asthma.

Elevated levels of this protein have been found in patients with the disease.

Study of Hutterites

Researchers led by Carole Ober of the University of Chicago focused their asthma research on SNPs associated with increased blood levels of YKL-40.

The initial studies were carried out in the Hutterites, a genetically isolated religious community in South Dakota. This group provides an ideal community for genetic studies because their family relationships are all known and they share the same environmental conditions.

Blood levels of YKL-40 in the Hutterites were most strongly associated with the SNP rs4950928. In previous studies, the G version of this SNP has been shown to reduce blood levels of the protein by interfering with its production.

Ober et al. found that in the Hutterites, the C version of rs4950928 was associated with higher blood levels of YL-40 and was also significantly associated with asthma.

Impact on Drug Development

The researchers confirmed their asthma findings in two other groups with European ancestry, one from Chicago and another from Freiberg, Germany. People with two copies of the C version of rs4950928 had 1.85 times greater odds of having asthma than people with only one copy of the C version or two copies of the G version. About 69% percent of people with European ancestry are estimated to have two copies of the C version.

In a group of six-year-olds from Madison, WI, no association was found between rs4950928 and asthma, although the C version of this SNP was associated with increased blood levels of YKL-40. This may mean that the causes of asthma are different in children younger than six years of age compared to older children and adults.

Ober said that this research could have a significant impact on drug development.

“For some people, if you block YKL-40 you might dramatically reduce the severity of the disease. Knowing the genotype at SNP-131C [rs4950928] might identify those most likely to benefit from such a treatment,” she said.