Gene-environment and gene-gene interaction studies in the molecular genetic analysis of asthma and atopy.

Asthma is a complex trait for which genetic predisposition is fundamental in disease aetiology, but poorly understood. Unravelling the genetic aetiology is complicated by the tremendous influence of the environment over disease expression. For this reason, asthma is multifactorial, in that disease expression is influenced by interactions between multiple major and minor genes, and modulated by interacting non-genetic factors (e.g. environment). 'Parent of origin' effects may be both genetic and environmental in aetiology, and have been observed in a number of population studies on asthma. The primary focus of this review is to evaluate the current approaches used in identifying the interrelationship between (1) certain environmental factors (e.g. allergen exposure, maternal inheritance) and genetic susceptibility to asthma and its associated phenotypes; and (2) candidate genes in chromosomal regions that have been linked to asthma and atopy in ongoing, molecular genetics studies.