Genetics of Asthma and Bronchial Hyperresponsiveness

BACKGROUND:

The development of asthma requires exposure to inciting agents such as allergens and environmental pollutants, as well as the presence of host or genetic factors. Understanding the genetics of bronchial hyperresponsiveness (BHR) and allergy will delineate mechanisms that are important in the pathogenesis and therapy of asthma. While both genetic and environmental factors and their interactions are felt to be important, their precise role is not fully understood.

DESIGN NARRATIVE:

The probands are from the 'asthma' center Beatrixoord in Haren, The Netherlands which was started in 1962. In collaboration with Dr Dirkje Postma of Holland, data are available on approximately 1200 patients who were first studied in 1963-1970 using the same protocol. Family studies of the children and grandchildren of these original probands are underway. At this time, 85 complete families have been characterized and clinical data and DNA are available for analysis in Baltimore. Families are being ascertained so that the investigators can test the fit of genetic models through segregation analyses. The major aim of the study is to identify major genes for bronchial hyperresponsiveness (BHR) and asthma by linkage with highly polymorphic DNA markers. Since allergy is commonly associated with asthma, a second goal of the study is to identify major genes for atopy using similar linkage studies. Allergic factors under study include skin test reactivity to common allergens, serum total and specific IgE levels, and blood eosinophilia. Complex segregation analysis will be performed separately for asthma, BHR and allergy. The most parsimonious model from the segregation analysis will be used for linkage analysis. Initially, candidate regions of the genome will be evaluated. Then, a systematic search of the genome will be performed using highly polymorphic informative makers. When a linkage is detected, candidate genes in that specific area will be studied.

The study was renewed in FY 1999 and in FY 2004 to: further characterize asthma and closely related phenotypes; perform genetic modeling (complex segregation analysis) using one and two locus models as well as bivariate segregation analysis; complete the genome wide screen; fine map regions of interest and identify candidate genes, perform linkage disequilibrium and haplotype sharing analyses; and perform case control analysis of susceptibility and severity candidate genes for asthma.