In the first search of the entire human genome in African Americans, Caucasians, and Hispanics with asthma, researchers supported by the National Heart, Lung, and Blood Institute (NHLBI) have found evidence for linkage of asthma-susceptibility genes to six previously-unreported chromosomal regions. Evidence for linkage was also detected in 5 regions previously reported to be linked to asthma-associated traits, such as bronchial hyperresponsivity and allergic sensitivity. Of the 11 chromosomal regions identified, all but one were unique to only one racial or ethnic group, suggesting that the relative importance of specific asthma-susceptibility genes and the effects of environmental exposures may vary by race or ethnicity.
The report, from the NHLBI Collaborative Study on the Genetics of Asthma (CSGA), appears in the April issue of Nature Genetics.
According to NHLBI Director Dr. Claude Lenfant, "This is an intriguing study. It not only brings us one step closer to identifying all the important genes that contribute to the development of asthma, but it also provides a possible explanation for the substantial differences in disease prevalence and severity that we have observed among different racial and ethnic groups in the U.S."
"Of course," he added, "these findings must be replicated in additional families with asthma."
The investigators currently are analyzing the 11 chromosomal regions in a new set of families to try to replicate the findings.
The prevalence of asthma is greater for blacks (6.1 percent) than for whites (5.0 percent), while in Hispanics, it ranges from a low of 2.7 percent among Mexican-American children living in the Southwest to 11.2 percent for Puerto Rican children living in New York City. Both hospitalization and death rates for blacks are nearly triple those of whites.
In the study, investigators at the 4 CSGA centers analyzed data on 380 children and adults with asthma (117 African Americans, 215 Caucasians, and 48 Hispanics). Each of the 140 families involved in the current analysis had at least 2 siblings with established asthma.
The CSGA centers are the University of Chicago, the Johns Hopkins University, the University of Maryland, and the University of Minnesota. The gene mapping was performed by the NHLBI Mammalian Genotyping Service in Marshfield, WI.
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