Hitomi Yuki, Aiba Yoshihiro, Ueno Kazuko, Nishida Nao, Kawai Yosuke, Kawashima Minae, Yasunami Michio, Gervais Olivier, Ito Masahiro, Cordell Heather J, Mells George F, Nagasaki Masao, Tokunaga Katsushi, Tsuiji Makoto, Nakamura Minoru
Department of Microbiology, Hoshi University School of Pharmacy and Pharmaceutical Sciences, Tokyo, Japan.
Clinical Research Center, National Hospital Organization (NHO) Nagasaki Medical Center, Omura, Japan.
J Autoimmun. 2022 Jan;126:102775. doi: 10.1016/j.jaut.2021.102775. Epub 2021 Dec 2.
Primary biliary cholangitis (PBC) is a chronic cholestatic autoimmune liver disease that appears to be strongly influenced by genetic factors. Recently, an international meta-analysis of genome-wide association studies (GWAS) identified CC-Motif Chemokine Receptor-6 (CCR6) and FGFR1 Oncogene-Partner (FGFR1OP) as PBC-susceptibility genes. However, the lead single nucleotide polymorphisms (SNPs) of CCR6/FGFR1OP showed low linkage disequilibrium with each other in East Asian and European populations. Additionally, the primary functional variants and the molecular mechanisms responsible for PBC-susceptibility remain unclear. Here, among the PBC-susceptibility SNPs identified by high-density association mapping in our previous meta-GWAS (Patients: n = 10,516; healthy controls: n = 20,772) within the CCR6/FGFR1OP locus, rs9459874 and rs1012656 were identified as primary functional variants. These functional variants accounted for the effects of GWAS-identified lead SNPs in CCR6/FGFR1OP. Additionally, the roles of rs9459874 and rs1012656 in regulating FGFR1OP transcription and CCR6 translation, respectively, were supported by expression quantitative trait loci (eQTL) analysis and gene editing technology using the CRISPR/Cas9 system. Immunohistochemistry showed higher expression of CCR6 protein in the livers of patients with PBC than in those of a non-diseased control. In conclusion, we identified primary functional variants in CCR6/FGFR1OP and revealed the molecular mechanisms by which these variants confer PBC-susceptibility in an eQTL-dependent or -independent manner. The approach in this study is applicable for the elucidation of the pathogenesis of other autoimmune disorders in which CCR6/FGFR1OP is known as a susceptibility locus, as well as PBC.
原发性胆汁性胆管炎（PBC）是一种慢性胆汁淤积性自身免疫性肝病，似乎受到遗传因素的强烈影响。最近，一项全基因组关联研究（GWAS）的国际荟萃分析确定CC基序趋化因子受体6（CCR6）和FGFR1癌基因伴侣（FGFR1OP）为PBC易感基因。然而，CCR6/FGFR1OP的主要单核苷酸多态性（SNP）在东亚和欧洲人群中彼此之间的连锁不平衡较低。此外，导致PBC易感性的主要功能变异和分子机制仍不清楚。在此，在我们之前的荟萃GWAS（患者：n = 10516；健康对照：n = 20772）通过高密度关联图谱鉴定的PBC易感SNP中，CCR6/FGFR1OP基因座内的rs9459874和rs1012656被确定为主要功能变异。这些功能变异解释了GWAS确定的CCR6/FGFR1OP中主要SNP的效应。此外，使用CRISPR/Cas9系统的表达定量性状位点（eQTL）分析和基因编辑技术分别支持了rs9459874和rs1012656在调节FGFR1OP转录和CCR6翻译中的作用。免疫组织化学显示，PBC患者肝脏中CCR6蛋白的表达高于非疾病对照者。总之，我们在CCR6/FGFR1OP中鉴定了主要功能变异，并揭示了这些变异以eQTL依赖或独立方式赋予PBC易感性的分子机制。本研究中的方法适用于阐明其他自身免疫性疾病的发病机制，在这些疾病中CCR6/FGFR1OP被认为是一个易感基因座，PBC也是如此。
