A tiny variation in a gene known as CHI3L1 increases susceptibility to asthma, bronchial hyperresponsiveness, and a decline in lung function, researchers report.
In 1996 and 1997, scientists from the University of Chicago Medical Center gathered clinical data about asthma and blood samples from more than 700 members of the Hutterite communities, a relatively homogenous group around South Dakota. Recently, a group from Yale University showed that, on average, patients with asthma had higher levels of the protein YKL-40 in their blood than people without asthma and that those with more severe asthma had even higher levels.
Working with the Yale laboratory, the Chicago Medical Center team found that mean YKL-40 levels were also increased among Hutterites with asthma or hyperresponsive airways. They also showed that these elevated YKL-40 levels were handed down from generation to generation, indicating that differences between individuals were due nearly entirely to genetic differences.
Looking for variations in the CHI3L1 gene on chromosome 1 that codes for YKL-40, the researchers found that those inheriting two copies of a C at -131 had higher YKL-40 levels and an asthma prevalence of 0.20. Those with CG had intermediate YKL-40 levels and an asthma prevalence of 0.12. Those with GG had the lowest YKL-40 levels and a prevalence of only 0.08. These results were then confirmed in two other clinical samples.
Investigators from the University of Wisconsin, Madison, the University of South Dakota Medical School, and University of Freiburg were also involved in the study. The study is published early online in the New England Journal of Medicine.