Genome-wide association studies (GWAS) and their importance in asthma

Asthma is a complex disease determined by the interaction of different genes and environmental factors. The first genetic investigations in asthma were candidate gene association studies and linkage studies. In recent years research has focused on association studies that scan the entire genome without any prior conditioning hypothesis: the so-called genome-wide association studies (GWAS). The first GWAS was published in 2007, and described a new locus associated to asthma in chromosome 17q12-q21, involving the ORMDL3, GSDMB and ZPBP2 genes (a description of the genes named in the manuscript are listed in Table 1). None of these genes would have been selected in a classical genetic association study since it was not known they could be implicated in asthma. To date, a number of GWAS studies in asthma have been made, with the identification of about 1000 candidate genes. Coordination of the different research groups in international consortiums and the application of new technologies such as new generation sequencing will help discover new implicated genes and improve our understanding of the molecular mechanisms underlying the disease

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Implications of cytokine genes in allergic asthma

Asthma is a complex disease involving numerous mediator molecules and effector cells, in combination with a range of environmental determining factors. Cytokines play a key role in the physiopathological mechanisms of asthma; the study of the structure, regulation and variations of the genes that encode for these molecules is therefore crucial. Cytokines have extremely diverse roles, and exert effects both as activators and inhibitors of the innate and adaptive immune response. Certain modifications in the expression or structure of these molecules, resulting from the presence of polymorphisms, may give rise to deregulation of the mentioned effects, and therefore to a predisposition to develop concrete asthma phenotypes

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The prostaglandin D2 receptor (PTGDR) gene in asthma and allergic diseases

The prostaglandin D2 receptor (PTGDR) gene has been associated to asthma and related phenotypes by linking and association studies. Functional studies involving animal models and other expression studies based on in vitro cell models also point to a possible role of polymorphisms in the promoter region, in the differential binding of transcription factors, and thus in PTGDR expression, which appear to be associated to the development of asthma or of susceptibility to the disease

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Tryptase: Genetic and functional considerations

Tryptase is one of the main proteases located in the secretory granules of the mast cells, and is released through degranulation. It is therefore assumed to play an important role in inflammatory and allergic processes. Four genes are known to encode for these enzymes, with different alleles that give rise to different types of tryptases. The term "tryptase" generally refers to beta-tryptase, which in vivo is a heterotetramer, possessing a structure of vital importance for enabling drug and substrate access to the active site of the molecule. Tryptase has been reported to possess antagonistic functions, since it plays an important role both in inflammatory phenomena and as a protector against infection. In allergic processes it is associated to bronchial hyperresponsiveness in asthmatic patients, where PAR-2 is of great importance as an airway receptor. Lastly, the genes that encode for tryptase are highly polymorphic and complex. As a result, it is important to establish a relationship between genotype and phenotype in disorders such as asthma, and to identify mutations that are presumably of pharmacological relevance(AU)

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