Variants of thymic stromal lymphopoietin and its receptor associate with eosinophilic esophagitis

Abstract

Background: The genetic cause of eosinophilic esophagitis (EE) has been largely unexplored until a recent genome-wide association study identified a disease susceptibility locus on 5q22, a region that harbors the thymic stromal lymphopoietin (TSLP) gene. However, it is unclear whether the observed genetic associations with EE are disease-specific or confounded by the high rate of allergy in patients with EE. In addition, the genetic contributions of other allergy-associated genes to EE risk have not been explored.

Objective: We aimed to delineate single nucleotide polymorphisms (SNPs) that associated with EE apart from allergy.

Methods: We used a custom array containing 738 SNPs in 53 genes implicated in allergic responses, immune responses, or both to genotype 220 allergic or 246 nonallergic control subjects and a discovery cohort of 170 patients with EE. We replicated a statistically significant SNP association in an independent case-control cohort and examined the induction of the candidate gene in primary esophageal epithelial cells.

Results: A single SNP residing in the TSLP gene reached Bonferroni linkage disequilibrium-adjusted significance but only when patients with EE were compared with allergic control subjects (rs10062929; P = 4.11 x 10(-5); odds ratio, 0.35). A nonsynonymous polymorphism in the thymic stromal lymphopoietin receptor (TSLPR) gene on Xp22.3 and Yp11.3 was significantly associated with disease only in male patients with EE. Primary esophageal epithelial cells expressed TSLP mRNA after Toll-like receptor 3 stimulation.

Conclusion: These data collectively identify TSLP as a candidate gene critically involved in EE susceptibility beyond its role in promoting T(H)2 responses.

Figure 1. Associations of TSLP SNPs with EE are independent of allergy phenotypes

Upper panel, the associated −log₁₀ P-values for the genotyped TSLP SNPs from each analysis (EE vs. allergic or non-allergic controls) are plotted by relative base pair location. The dashed line represents the Bonferroni threshold for significance (P = 3 × 10⁻⁴). Lower panel, the TSLP SNPs reside within an approximate 8 kilobase interval on 5q22.1 encoding the TSLP gene isoforms (NM_ 033035 and NM_138551). Represented are exons (white boxes), introns (bold lines), and untranslated regions (gray boxes).

Figure 2. A non-synonymous SNP in the TSLPR associates with EE in a gender-specific manner

A non-synonymous SNP (rs36133495) in the TSLPR, which results in an Ala to Val coding change shows a gender-based association with increased disease risk in male EE patients, with Val/Val and Ala/Val individuals at higher risk (OR = 2.05) compared to Ala/Ala individuals. Genotyped were 199 male EE patients and 78 male normal (NL) controls.

Figure 3. TLR signaling stimulates TSLP expression in primary esophageal epithelial cells

Treatment of primary esophageal epithelial cells with the TLR3 agonist poly I:C induces a robust increase in TSLP mRNA levels. The data shown are the mean ± SEM from 4–5 independent experiments performed in duplicate (*, P < 0.05; **, P < 0.01; ***, P < 0.001).