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Prevalence of genetic polymorphisms in atopic families

University of British Columbia

Genetic susceptibility to atopy and asthma is due to multiple genes interacting with each other and with environment factors. Variants in regulatory or coding regions of specific genes have been associated with atopy and asthma. Polymorphisms at position -308 in the promoter region of the TNFα gene, -590 in the promoter region of the IL4 gene and amino acid position 237 of the FceRiβ gene have been reported with increased frequency in asthmatic as opposed to control subjects. The aim of this thesis was to determine the predictive value of these polymorphisms in the development of childhood atopy and asthma and whether any of these polymorphisms were associated with atopy and asthma in adult subjects. A prospective cohort including 493 infants born into atopic families was selected. Cord blood was collected at birth. Each infant was assessed at 12 months for respiratory symptoms and skin prick tests for 14 common allergens were performed. DNA was extracted for infants and their parents. Polymerase chain reaction based techniques were used to genotype all the infants and their parents for TNFα-308, IL4-590 and FceRip polymorphisms. In whites, there was a significant association of the IL4-590 polymorphism with "probable asthma"; there were no association of the TNFα-308 and FceRiβ polymorphisms with asthma or atopy in either the parents or their children. Therefore, IL4-590 polymorphism may be a risk factor for the development of asthma while TNFα-308 and FceRiβ polymorphisms had no predictive value for atopic diseases in whites. In the whole infant population, we found the allele frequency of the IL4-590 polymorphism was significantly higher than that in the non-atopic, non-asthmatic controls (p=0.04) or in the general population (p=0.01). The prevalence of atopy was significantly higher in infants with the T allele of IL4-590 polymorphism (IL4-590*T) than in those without this allele (p=0.002). The allele frequency of IL4-590*T was significantly higher in Orientals than that in whites (p<0.0001). To avoid a false positive association caused by population admixture, the transmission/disequilibrium test was performed. A borderline association of IL4-590*T with atopy (p=0.07) was detected. This adds power to our suggestion that IL4-590*T may play a role in the pathogenesis of atopy.

Thesis/Dissertation

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2009-06-11

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http://hdl.handle.net/2429/9002

Experimental Medicine

University of British Columbia

UBCV

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