Melchiotti Rossella, Puan Kia Joo, Andiappan Anand Kumar, Poh Tuang Yeow, Starke Mireille, Zhuang Li, Petsch Kerstin, Lai Tuck Siong, Chew Fook Tim, Larbi Anis, Wang De Yun, Poidinger Michael, Rotzschke Olaf
SIgN (Singapore Immunology Network), A*STAR (Agency for Science, Technology and Research), Singapore 138648, Singapore.
BMC Med Genet. 2014 Jun 27;15:73. doi: 10.1186/1471-2350-15-73.
Extracellular ATP is a pro-inflammatory molecule released by damaged cells. Regulatory T cells (Treg) can suppress inflammation by hydrolysing this molecule via ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1), also termed as CD39. Multiple studies have reported differences in CD39+ Treg percentages in diseases such as multiple sclerosis, Hepatitis B and HIV-1. In addition, CD39 polymorphisms have been implicated in immune-phenotypes such as susceptibility to inflammatory bowel disease and AIDS progression. However none of the studies published so far has linked disease-associated variants with differences in CD39 Treg surface expression. This study aims at identifying variants affecting CD39 expression on Treg and at evaluating their association with allergic rhinitis, a disease characterized by a strong Treg involvement.
Cohorts consisting of individuals of different ethnicities were employed to identify any association of CD39 variants to surface expression. Significant variant(s) were tested for disease association in a published GWAS cohort by one-locus and two-locus genetic analyses based on logistic models. Further functional characterization was performed using existing microarray data and quantitative RT-PCR on sorted cells.
Our study shows that rs7071836, a promoter SNP in the CD39 gene region, affects the cell surface expression on Treg cells but not on other CD39+ leukocyte subsets. Epistasis analysis revealed that, in conjunction with a SNP upstream of the FAM134B gene (rs257174), it increased the risk of allergic rhinitis (P = 1.98 × 10-6). As a promoter SNP, rs257174 controlled the expression of the gene in monocytes but, notably, not in Treg cells. Whole blood transcriptome data of three large cohorts indicated an inverse relation in the expression of the two proteins. While this observation was in line with the epistasis data, it also implied that a functional link must exist. Exposure of monocytes to extracellular ATP resulted in an up-regulation of FAM134B gene expression, suggesting that extracellular ATP released from damaged cells represents the connection for the biological interaction of CD39 on Treg cells with FAM134B on monocytes.
The interplay between promoter SNPs of CD39 and FAM134B results in an intercellular epistasis which influences the risk of a complex inflammatory disease.
细胞外ATP是受损细胞释放的一种促炎分子。调节性T细胞（Treg）可通过外切核苷酸三磷酸二磷酸水解酶1（ENTPD1，也称为CD39）水解该分子来抑制炎症。多项研究报告了在诸如多发性硬化症、乙型肝炎和HIV-1等疾病中CD39 + Treg百分比的差异。此外，CD39多态性与免疫表型有关，如对炎症性肠病的易感性和艾滋病进展。然而，迄今为止发表的研究均未将疾病相关变体与CD39 Treg表面表达差异联系起来。本研究旨在鉴定影响Treg上CD39表达的变体，并评估它们与变应性鼻炎的关联，变应性鼻炎是一种Treg大量参与的疾病。
使用由不同种族个体组成的队列来鉴定CD39变体与表面表达的任何关联。通过基于逻辑模型的单基因座和双基因座遗传分析，在已发表的全基因组关联研究（GWAS）队列中测试显著变体与疾病的关联。使用现有的微阵列数据和对分选细胞进行定量逆转录聚合酶链反应（qRT-PCR）进行进一步的功能表征。
我们的研究表明，rs7071836，CD39基因区域的一个启动子单核苷酸多态性（SNP），影响Treg细胞上的细胞表面表达，但不影响其他CD39 +白细胞亚群。上位性分析显示，与FAM134B基因上游的一个SNP（rs257174）一起，它增加了变应性鼻炎的风险（P = 1.98×10-6）。作为一个启动子SNP，rs257174控制该基因在单核细胞中的表达，但值得注意的是，在Treg细胞中不控制。三个大型队列的全血转录组数据表明这两种蛋白的表达呈负相关。虽然这一观察结果与上位性数据一致，但也意味着必须存在功能联系。单核细胞暴露于细胞外ATP导致FAM134B基因表达上调，表明受损细胞释放的细胞外ATP代表了Treg细胞上的CD39与单核细胞上的FAM134B之间生物学相互作用的联系。
CD39和FAM134B启动子SNP之间的相互作用导致细胞间上位性，影响复杂炎症性疾病的风险。
