Collaborative Studies on the Genetics of Asthma (CSGA)

BACKGROUND: Asthma is a respiratory disease characterized by variable airways obstruction, airways inflammation and bronchial hyperresponsiveness (BHR). There are recent increases in asthma mortality and prevalence in the US, especially in African-Americans. Multiple studies suggest that both genetic and environmental factors are important in asthma susceptibility. The study was recommended by the Pulmonary Diseases Advisory Committee at its February 1991 meeting and given concept approval by the May 1991 National Heart, Lung, and Blood Advisory Council. The Request for Applications was released in October 1992. DESIGN NARRATIVE: The CSGA was composed of five centers (Johns Hopkins University, University of Chicago, University of Maryland, University of Minnesota, and a data coordinating center at Wake Forest). At each center, families were ascertained through two siblings with asthma. All family members were characterized with spirometry, bronchial responsiveness to methacholine or reversibility testing, skin-tests and questionnaire data. The initial genome screen was completed on the first 237 sib pairs from three racial groups (African-American, Caucasian and Hispanic), and genotyping on the remaining family members and families was completed before the study was renewed in 1997. Therefore, the initial aim of the CSGA to map susceptibility regions was completed, with detection of several novel chromosomal regions, and replication of several regions previously linked to associated phenotypes. In order to determine the importance of these regions in asthma susceptibility and the impact of environmental rink factors, the investigators l) evaluated the evidence for linkage in the complete CSGA data using 2-point, multipoint and multilocus approaches for asthma and associated phenotypes (including BHR, total serum IgE and skin test reactivity to standardized allergens); 2) performed fine mapping studies of regions using additional genetic markers to obtain a \< 2 cM map; 3) identified candidate genes and novel sequence variants; and 4) characterized a patient population with asthma to study identified variants with respect to asthma severity and bronchial inflammation. These studies allowed identification of asthma susceptibility genes and their variants, interactions with other genes and environmental risk factors, as well as provided insight for the development of improved treatment and ultimate prevention of asthma.