Genetics in Asthma
Asthma is a complex disease determined by the interaction between genetic and environmental factors. The heritability of asthma is estimated to be more than 50%. The search for genes with genomic variants associated with asthma has been greatly advanced by hypothesis-driven candidate gene association studies and hypothesis-free genome-wide association studies (GWASs). The genes identified by the hypothesis-driven approach are roughly classified into four types of functional group: (1) innate immunity and immunoregulation, (2) differentiation and regulation of T-helper 2 cells, (3) airway epithelial mucosal immunity, and (4) airway remodeling and lung function. Although the majority of the variants have been identified by the hypothesis-driven approach, novel genes and pathways associated with asthma have been successively clarified by GWASs. Nonetheless, these genomic variants explain only a small proportion of asthma heritability. This is partly due to the phenotypic heterogeneity of asthma, epistatic gene-gene interactions, gene-environment interactions, and epigenetic effects. Further elucidation of the causal variants can be achieved by GWASs that limit participants to those with distinct asthma phenotypes and by integrative applications of genome-wide epistatic and epigenetic approaches. Understanding of the genetic profiles of asthma pathogenesis contributes to individualized disease prevention as well as to development of new therapies.
KeywordsAssociation study Epigenetics Epistasis Gene-environment interaction
We would like to thank F. Miyamasu, associate professor of English for Medical Purposes, Medical English Communications Center, University of Tsukuba, for grammatical review and advice.
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