Zhao Jian, Giles Brendan M, Taylor Rhonda L, Yette Gabriel A, Lough Kara M, Ng Han Leng, Abraham Lawrence J, Wu Hui, Kelly Jennifer A, Glenn Stuart B, Adler Adam J, Williams Adrienne H, Comeau Mary E, Ziegler Julie T, Marion Miranda, Alarcón-Riquelme Marta E, Alarcón Graciela S, Anaya Juan-Manuel, Bae Sang-Cheol, Kim Dam, Lee Hye-Soon, Criswell Lindsey A, Freedman Barry I, Gilkeson Gary S, Guthridge Joel M, Jacob Chaim O, James Judith A, Kamen Diane L, Merrill Joan T, Sivils Kathy Moser, Niewold Timothy B, Petri Michelle A, Ramsey-Goldman Rosalind, Reveille John D, Scofield R Hal, Stevens Anne M, Vilá Luis M, Vyse Timothy J, Kaufman Kenneth M, Harley John B, Langefeld Carl D, Gaffney Patrick M, Brown Elizabeth E, Edberg Jeffrey C, Kimberly Robert P, Ulgiati Daniela, Tsao Betty P, Boackle Susan A
Division of Rheumatology, Department of Medicine, University of California at Los Angeles, Los Angeles, California, USA.
Division of Rheumatology, University of Colorado School of Medicine, Aurora, Colorado, USA.
Ann Rheum Dis. 2016 Jan;75(1):242-52. doi: 10.1136/annrheumdis-2014-205584. Epub 2014 Sep 1.
Systemic lupus erythematosus (SLE; OMIM 152700) is characterised by the production of antibodies to nuclear antigens. We previously identified variants in complement receptor 2 (CR2/CD21) that were associated with decreased risk of SLE. This study aimed to identify the causal variant for this association.
Genotyped and imputed genetic variants spanning CR2 were assessed for association with SLE in 15 750 case-control subjects from four ancestral groups. Allele-specific functional effects of associated variants were determined using quantitative real-time PCR, quantitative flow cytometry, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-PCR.
The strongest association signal was detected at rs1876453 in intron 1 of CR2 (pmeta=4.2×10(-4), OR 0.85), specifically when subjects were stratified based on the presence of dsDNA autoantibodies (case-control pmeta=7.6×10(-7), OR 0.71; case-only pmeta=1.9×10(-4), OR 0.75). Although allele-specific effects on B cell CR2 mRNA or protein levels were not identified, levels of complement receptor 1 (CR1/CD35) mRNA and protein were significantly higher on B cells of subjects harbouring the minor allele (p=0.0248 and p=0.0006, respectively). The minor allele altered the formation of several DNA protein complexes by EMSA, including one containing CCCTC-binding factor (CTCF), an effect that was confirmed by ChIP-PCR.
These data suggest that rs1876453 in CR2 has long-range effects on gene regulation that decrease susceptibility to lupus. Since the minor allele at rs1876453 is preferentially associated with reduced risk of the highly specific dsDNA autoantibodies that are present in preclinical, active and severe lupus, understanding its mechanisms will have important therapeutic implications.
系统性红斑狼疮（SLE；OMIM 152700）的特征是产生针对核抗原的抗体。我们之前鉴定出补体受体2（CR2/CD21）中的变异与SLE风险降低相关。本研究旨在确定这种关联的因果变异。
对来自四个祖先群体的15750例病例对照受试者中跨越CR2的基因分型和推断的遗传变异进行SLE关联评估。使用定量实时PCR、定量流式细胞术、电泳迁移率变动分析（EMSA）和染色质免疫沉淀（ChIP）-PCR确定相关变异的等位基因特异性功能效应。
在CR2内含子1中的rs1876453处检测到最强的关联信号（pmeta=4.2×10⁻⁴，OR 0.85），特别是当受试者根据双链DNA自身抗体的存在进行分层时（病例对照pmeta=7.6×10⁻⁷，OR 0.71；仅病例pmeta=1.9×10⁻⁴，OR 0.75）。虽然未发现对B细胞CR2 mRNA或蛋白质水平的等位基因特异性效应，但携带次要等位基因的受试者的B细胞上补体受体1（CR1/CD35）mRNA和蛋白质水平显著更高（分别为p=0.0248和p=0.0006）。次要等位基因通过EMSA改变了几种DNA-蛋白质复合物的形成，包括一种含有CCCTC结合因子（CTCF）的复合物，这一效应通过ChIP-PCR得到证实。
这些数据表明CR2中的rs1876453对基因调控具有远距离效应，可降低狼疮易感性。由于rs1876453处的次要等位基因优先与临床前、活动期和重度狼疮中存在的高度特异性双链DNA自身抗体风险降低相关，了解其机制将具有重要的治疗意义。
