State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.
ACT Center for Tobacco Treatment, Education and Research, Department of Otolaryngology and Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
Transl Psychiatry. 2018 Apr 18;8(1):83. doi: 10.1038/s41398-018-0130-x.
Nicotine dependence (ND) is a worldwide health problem. Numerous genetic studies have demonstrated a significant association of variants in nicotinic acetylcholine receptors (nAChRs) with smoking behaviors. However, most of these studies enrolled only subjects of European or African ancestry. In addition, although an increasing body of evidence implies a causal connection of single-nucleotide polymorphisms (SNPs) and epigenetic regulation of gene expression, few studies of this issue have been reported. In this study, we performed both association and interaction analysis for 67 SNPs in CHRNA3-A5, CHRNA7, CHRNB2, and CHRNB4 with ND in a Chinese Han population (N = 5055). We further analyzed cis-mQTL for the three most significant SNPs and 5580 potential methylation loci within these target gene regions. Our results indicated that the SNPs rs1948 and rs7178270 in CHRNB4 and rs3743075 in CHRNA3 were significantly associated with the Fagerström Test for Nicotine Dependence (FTND) score (p = 6.6 × 10; p = 2.0 × 10, and p = 7.0 × 10, respectively). Haplotype-based association analysis revealed that two major haplotypes, T-G and C-A, formed by rs3743075-rs3743074 in CHRNA3, and other two major haplotypes, A-G-C and G-C-C, formed by rs1948-rs7178270-rs17487223 in CHRNB4, were significantly associated with the FTND score (p ≤ 8.0 × 10). Further, we found evidence for the presence of significant interaction among variants within CHRNA3/B4/A5, CHRNA4/B2/A5, and CHRNA7 in affecting ND, with corresponding p values of 5.8 × 10, 8.0 × 10, and 0.012, respectively. Finally, we identified two CpG sites (CpG_2975 and CpG_3007) in CHRNA3 that are significantly associated with three cis-mQTL SNPs (rs1948, rs7178270, rs3743075) in the CHRNA5/A3/B4 cluster (p ≤ 1.9 × 10), which formed four significant CpG-SNP pairs in our sample. Together, we revealed at least three novel SNPs in CHRNA3 and CHRNB4 to be significantly associated with the FTND score. Further, we showed that these significant variants contribute to ND via two methylated sites, and we demonstrated significant interaction affecting ND among variants in CHRNA5/A3/B4, CHRNA7, and CHRNA4/B2/A5. In sum, these findings provide robust evidence that SNPs in nAChR genes convey a risk of ND in the Chinese Han population.
尼古丁依赖（ND）是一个全球性的健康问题。大量的遗传研究表明，烟碱型乙酰胆碱受体（nAChRs）中的变异与吸烟行为有显著关联。然而，这些研究大多只招募了欧洲或非洲血统的受试者。此外，尽管越来越多的证据表明单核苷酸多态性（SNPs）和基因表达的表观遗传调控之间存在因果关系，但关于这个问题的研究报告很少。在这项研究中，我们对中国汉族人群中 CHRNA3-A5、CHRNA7、CHRNB2 和 CHRNB4 中的 67 个 SNPs 与 ND 进行了关联和交互分析（N=5055）。我们进一步分析了这三个目标基因区域内的三个最显著的 SNPs 和 5580 个潜在的甲基化位点的顺式-mQTL。我们的结果表明，CHRNB4 中的 rs1948 和 rs7178270 以及 CHRNA3 中的 rs3743075 与尼古丁依赖测试（FTND）评分显著相关（p=6.6×10；p=2.0×10 和 p=7.0×10）。基于单倍型的关联分析显示，由 CHRNA3 中的 rs3743075-rs3743074 形成的两个主要单倍型，T-G 和 C-A，以及由 CHRNB4 中的 rs1948-rs7178270-rs17487223 形成的另外两个主要单倍型，A-G-C 和 G-C-C，与 FTND 评分显著相关（p≤8.0×10）。此外，我们发现 CHRNA3/B4/A5、CHRNA4/B2/A5 和 CHRNA7 内变异之间存在显著的相互作用，与 ND 相关，对应的 p 值分别为 5.8×10、8.0×10 和 0.012。最后，我们鉴定了 CHRNA3 中两个 CpG 位点（CpG_2975 和 CpG_3007），它们与 CHRNA5/A3/B4 簇中的三个顺式-mQTL SNPs（rs1948、rs7178270、rs3743075）显著相关（p≤1.9×10），在我们的样本中形成了四个显著的 CpG-SNP 对。综上所述，我们揭示了至少三个新的 SNPs 与 FTND 评分显著相关。此外，我们表明这些显著的变异通过两个甲基化位点导致 ND，并证明了 CHRNA5/A3/B4、CHRNA7 和 CHRNA4/B2/A5 中变异之间影响 ND 的显著相互作用。总之，这些发现为 nAChR 基因中的 SNPs 在中国汉族人群中导致 ND 的风险提供了有力的证据。
