中文摘要：

G蛋白偶联受体120（G—protein coupled receptor 120，GPR120）是脂肪组织中唯一高表达的一种长链不饱和脂肪酸受体，参与多种生理过程。DNA甲基化大多数发生在CpG含量丰富的区域（CpG岛），是一种介导基因在组织间差异性表达的重要表观遗传学修饰。为了研究CpG岛甲基化对GPR120在猪皮下f背部皮下）和内脏（大网）脂肪组织中mRNA表达量的影响，本实验采用qRT-PCR检测了金华猪（Susscrofa）（6月龄和7年）不同脂肪组织中GPR120 mRNA表达量。同时，利用在线预测软件分析了GPR120的DNA全序列（从第一外显子上游5000bp到最后一个外显子下游5000bp）的CpG岛分布，采用Sequenom MassArray甲基化DNA定量分析平台检测了CpG岛在不同脂肪组织中的甲基化状态，并用亚硫酸氢钠修饰后测序法（bisulfite-sequencing PCR，BSP）对Sequenom MassArray检测结果进行了验证。结果显示，在6月龄和7年两个时间点中，皮下组织中的脂肪体积都极显著高于大网的脂肪体积（P＜0．01），同时皮下组织中的GPR120表达量极显著高于大N（P＜0．01），与脂肪体积大小趋势一致。生物信息学方法预测出GPR120的DNA序列GC含量丰富，共含有5个CpG岛，依次位于基因的不同元件：5′非编码区、第1外显子、第2内含子和3’非编码区。甲基化分析结果显示，在两个时间点中位于第2内含子的CpG岛甲基化在皮下组织中显著高于大网（P＜0．05），并BSP实验结果验证了组织间的甲基化差异，其余4个CpG岛甲基化水平在组织间差异均不显著。第2内含子的CpG岛甲基化与基因表达差异趋势一致。本实验提供了在不同组织间整个基因范围内的DNA甲基化模式，结果表明GPR120富含丰富的CpG岛，其中基因内的CpG岛甲基化与其mRNA表达量正相关。本研究为揭示GPR120在组织间差异表达的表观遗传调控提供了理论基础。

英文摘要：

G-protein coupled receptor 120 （GPR120） is the only highly expressed G protein-coupled receptorin adipose tissues, which plays a critical role in various physiological processes. DNA methylation is an important epigenetic modification to mediate tissue-specific gene expression that mostly occurs in CpG-rich regions （CpG islands）. To study the effects of CpG island methylation for the expression levels of GPR120 in porcine （Sus scrofa）subcutaneous （backfat） and visceral （greater omentum） adipose tissues, this study used qRT-PCR to detect the relative expression levels of GPR120 in different adipose tissues of Jinhua pigs （6 months and 7 years old）, using CpG island searcher online software to scan the CpG island distribution across the whole GPR 120 DNA sequence （5 000 bp upstream of first exon to 5 000 bp downstream of last exon）, and detected the methylation status of CpG island in different adipose tissues using Sequenom MassArray methylation approach, using bisulfite-sequencing PCR （BSP） to validate the MassArray results. Results showed that compared with greater omentum, subcutaneous adipose tissue had a higher adipocyte volume both at 6 months and 7 years （P〈0.01）, and the relative transcript levels of GPR120 significantly higher expressed in subcutaneous adipose tissue than that of greater omentum （P〈0.01）, which was consistent with adipocyte volume differences. The DNA sequence of GPR120 had abundant GC contents, and contained five CpG islands which were predicted by bioinformatics analysis successively located within different genomic locations, that were the 5′ untranslated region, first exon, intron and 3′ untranslated region. The methylation status of CpG island within second intron in subcutaneous adipose tissue was significantly higher than that of greater omentum （P〈0.01） both at 6 months and 7 years, which was confirmed by the BSP approach, while the methylation levels of other 4 islands had no significant difference between subcutaneous adipose