Lack of association of CCR3 single nucleotide polymorphism with atopic dermatitis in Japanese population

Two-stage association study in Chinese Han identifies two independent associations in CCR1/CCR3 locus as candidate for Behçet's disease susceptibility

Previous GWAS studies from Turkey suggested a potential risk locus at CCR1/CCR3 for Behçet's disease. However, this locus did not reach the GWAS significance threshold and has not yet been examined in other ethnic populations. The current study aimed to explore whether this locus was associated with Behçet's disease in Chinese Han and the functional role of the identified variants. A two-stage association study was performed in 653 patients and 1,685 controls using the iPLEX system. Real-time PCR was performed to examine the expression level of CCR1 and CCR3 genes. Haplotype analysis was used to construct the haplotype block. Logistic regression analysis was applied to calculate the independence of multiple associations. Bonferroni correction was applied to account for multiple testing. First stage analysis showed that ten SNPs, located in 3'UTR, 5'UTR in CCR1 or 5'UTR in CCR3, were significantly associated with Behçet's disease (P(c) = 0.018 to 1.3 × 10(-3)). The associations of six SNPs within this locus are independent after control for the genetic effect of rs17282391 using logistic regression analysis. Haplotype analysis identified three associated haplotypes: H3 (GTGAC), H6 (CCATTA) and H9 (CGA) (P(c) = 0.04 to 7.79 × 10(-4)). Three SNPs rs13084057, rs13092160 and rs13075270 showed consistent association in replication and combining studies (replication P(c) = 5.31 × 10(-5) to 1.44 × 10(-5); combining P(c) = 2.76 × 10(-7) to 6.50 × 10(-8)). Interestingly, eQTLs database reveals that SNP rs13092160 is eQTLs SNP, suggesting that this SNP is likely to be functional SNP that directly affects gene expression. The expression of CCR1 and CCR3 was increased in individuals with the CT genotype of rs13092160 (P < 0.05). No significant difference was found for the mRNA level of CCR1 and CCR3 between Behçet's patients and controls. These findings strongly indicate CCR1/CCR3 as a novel locus underlying Behçet's disease.

The genetics of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a complex genetic disorder influenced by environmental factors. The mode of inheritance and genes involved are not clear.

RESULTS

This report here is focusing on the current progress in searching the disease-susceptibility genes of AD via both the linkage studies and candidate gene approaches. Genome-wide linkage studies have identified multiple susceptibility loci on 3q and 17q. Candidate region linkage studies identify other susceptibility loci on 5q23-33, 11q13, and 13q12-14. At least 28 candidate genes have to date been verified in association studies, but only association with genes of interleukin (IL)-4, IL-13, IL-4RA, mast cell chymase, and serine protease inhibitor, kazal-type 5 have been replicated in more than two different studies. More halpotype tests and family-based association studies may help to shed more light for the candidate gene approach.

CONCLUSION

Determining the candidate susceptibility genes for AD is not only helping understanding the pathophysiology but also affecting the response to therapy, which is important in pharmacogenetics. The effect of environmental trigger may also have to be considered to elucidate the real face of the disease.

Genetic susceptibility to atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with an increasing prevalence in industrialized countries. AD belongs to the group of allergic disorders that includes food allergy, allergic rhinitis, and asthma. A multifactorial background for AD has been suggested, with genetic as well as environmental factors influencing disease development. Recent breakthroughs in genetic methodology have greatly augmented our understanding of the contribution of genetics to susceptibility to AD. A candidate gene association study is a general approach to identify susceptibility genes. Fifty three candidate gene studies (50 genes) have identified 19 genes associated with AD risk in at least one study. Significant associations between single nucleotide polymorphisms (SNPs) in chemokines (chymase 1-1903A > G), cytokines (interleukin13 Arg144Gln), cytokine receptors (interleukin 4 receptor 1727G > A) and SPINK 1258G > A have been replicated in more than one studies. These SNPs may be promising for identifying at-risk individuals. SNPs, even those not strongly associated with AD, should be considered potentially important because AD is a common disease. Even a small increase in risk can translate to a large number of AD cases. Consortia and international collaborative studies, which may maximize study efficacy and overcome the limitations of individual studies, are needed to help further illuminate the complex landscape of AD risk and genetic variations.