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14-08-2011 | Genetics | Article

Multiple genetic loci associated with asthma in different ethnicities



MedWire News: Two genetic studies have identified new susceptibility loci in a group of ethnically diverse individuals with asthma.

In the first study, researchers identified five susceptibility loci in individuals of European-American, African-American, and Latino ancestry.

In addition, they identified a new asthma susceptibility locus in the PYHIN1 gene, an association that was specific to individuals of African descent.

"These results suggest that some asthma susceptibility loci are robust to differences in ancestry when sufficiently large samples sizes are investigated," write Dana Torgenson (University of Chicago, Illinois, USA) and colleagues in the journal Nature Genetics.

The researchers point out that while asthma is a common, complex disease, prevalence ranges across the different ethnic groups.

For example, the prevalence of asthma in the US among individuals descended from Europe is approximately 8%, but is nearly 13% in African-Americans. Among Latino-Americans, the prevalence of asthma ranges from 4% to 15%.

Past studies have suggested that genetic heritability accounts for 35% to 80% of the risk for developing asthma, yet few of these studies included ethnic minorities.

In their study, Torgenson and colleagues performed a large meta-analysis of North American genome-wide association studies that included 5416 European-American, African-American, and Latino-American individuals with asthma.

In addition, 12,649 individuals from the same ethnic groups were included in replication analyses.

Overall, the group identified five susceptibility loci, four of which were previously reported loci on chromosome 17q21, near the IL1RL1, TSLP, and IL33 genes.

Regarding the association with single nucleotide polymorphisms (SNPs) in PYH1N1, the researchers believe "this may be the first asthma susceptibility gene identified that is specific to populations of African descent."

Overall, the results highlight the importance of studying large datasets of diverse populations. The group notes that SNPs in the IL1RL1, TSLP, and IL33 genes did not reach genome-wide significance in any of the ethnicity-specific analyses.

In the second study, also published in Nature Genetics, Tomomitsu Hirota (RIKEN, Kanagawa, Japan) and colleagues performed a genome-wide association study in 7171 Japanese individuals with asthma and 27,912 healthy Japanese controls.

The researchers identified five loci associated with susceptibility to asthma, including SNPs at TSLP-WDR36 and the major histocompatibility complex. In addition to these previously reported loci, the group identified a USP38-GAB1 locus on chromosome 4q31, a locus on chromosome 10p14, and a locus in a gene-rich region on chromosome 12q13.

The most significant association with asthma was observed at the loci in the major histocompatibility complex region.

This locus, on chromosome 6p21, is situated close to another SNP that has been previously associated with pulmonary function in healthy adults, according to the researchers.

By MedWire Reporters

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