Genome wide association studies are extremely useful in trying to assess which genes are responsible for conditions caused by complex or unknown patterns. In a nutshell, hundreds of people with a particular condition (in this case, asthma) have their genomes compared. Researchers are looking for certain mutations/patterns like single nucleotide polymorphisms (SNPs) which are prevalent in those with the condition compared to control groups.
Dr. Hakon Hakonarson of The Children’s Hospital of Philadelphia and his colleagues have come across a particular region of interest on the long arm of chromosome 1 (specifically 1q31). Several SNPs in this region have been mapped to asthma in a variety of populations.
This locus contains DENND1B, a gene expressed by dendritic and natural killer cells, both important players in the immune response. I suppose that the strong correlation between asthma and mutations in this immune-related gene makes sense… especially if one considers allergies (primarily mediated by the immune system) as a potential cause of asthma.
More about the study can be read in the original article.