利用肥胖小鼠模型研究内环境对基因组甲基化影响的跨代遗传及稳定性

Epigenetic modifications are prone to being affected by environment, especially in the periods of gametogenesis and pre-implantation development. The changed epigenetic modification can inherit to the next generation and increase the risk of metabolic diseases in adult of offspring. But the underlying mechanism and hereditary stability remain not clear. We hypothesized that the altered epigenetic modifications caused by intra-environment, such as obesity in mammals could be inherited to the next generations by germ cells but the inheritance is instable. Obesity is a global metabolic disease and induces epigenetic changes in germ cells and embryos. Previous studies certify that offspring of obese parents have a higher risk of metabolic diseases in adulthood compared to normal body weight parents. We have found that DNA methylation patterns of leptin in oocytes of F0 and Peg3 in sperm of F1 were changed in obese mice induced by high-fat-diet. In the present study, we will use high-fat-diet induced mouse model to confirm this hypothesis. We will investigate the effects of obesity on global methylation, transcriptome and metabolism of F0-F3 mouse oocytes. Then we will confirm whether the abnormal methylation in oocyte could be inherited to the next generations, analyze the correlation between global methylation, transcriptome and metabolism in oocyte and discuss the possible mechanism underlying the abnormal global methylation. Furthermore, we will produce F1 mice by embryo transfer to investigate the role of obese intrauterine environment in global methylation alterations of F1 oocytes. This may clarify the methylation alteration in F1 oocytes is originated from F0 oocytes or obese intrauterine environment. To confirm the intergenerational stability, the metabolism of F1-F3 will be examined. The methylation status and expression of genes associated with metabolism in F1-F3 will also be investigated to reveal the possible mechanism underlying the abnormal metabolism. This study would be crucial for improving human reproductive health and reducing the risk of metabolic diseases in offspring.

表观遗传学修饰易受环境影响，尤其在生殖细胞形成和早期胚胎发育时期。异常的表观遗传修饰能够遗传给后代，使后代患代谢性疾病的风险升高。但环境引起的异常表观遗传修饰的遗传机制和遗传稳定性仍不清楚。我们推测内环境如肥胖等引起的哺乳动物表观遗传修饰异常能够通过生殖细胞遗传给后代但这种遗传是不稳定的。肥胖是全球性的代谢性疾病，对生殖细胞和早期胚胎发育中表观遗传修饰正常建立具有不利影响，而且导致后代患代谢性疾病的风险升高。我们前期研究发现肥胖改变了F0代小鼠卵母细胞leptin和F1精子Peg3甲基化状态。因此我们将利用高脂饲料诱导的肥胖小鼠模型研究肥胖对F0-F3代小鼠卵母细胞基因组甲基化水平、基因转录和代谢功能的影响及可能的机制；分析异常甲基化修饰通过生殖细胞在F1-F3代小鼠中的遗传情况及稳定性；通过胚胎移植探讨子宫环境在F1卵母细胞甲基化异常中的作用，阐明导致卵母细胞甲基化异常的机制。

肥胖是人类最常见的代谢性疾病之一，对心脑血管、糖脂代谢、子代健康等都具有重要影响。我们的前期研究发现肥胖导致卵子部分基因甲基化建立异常。本项目在前期研究的基础上深入研究了肥胖导致的卵子甲基化异常在后代间的遗传情况。本项目通过高脂饲料诱导构建肥胖小鼠模型，利用单细胞基因组甲基化测序技术和免疫荧光技术研究肥胖对卵子基因组甲基化的影响，结果显示肥胖导致卵子甲基化水平显著升高；高甲基化主要富集在启动子区域和外显子区域；通过差异甲基化分析鉴定出3571个差异甲基化区域DMRs，其中Hyper-DMRs 1625个，Hypo-DMRs 1936个，372个DMRs定位在基因启动子区域；利用KEGG对启动子区的DMRs相关基因进行富集分析，结果表明这些基因（55个）显著富集在代谢通路中，这说明肥胖导致的卵子甲基化异常可能是子代易患代谢综合征的重要原因；对部分启动子区DMRs甲基化进行深入分析发现部分卵子差异甲基化能够遗传到F1和F2肝脏，并引起基因表达改变；对F1和F2卵子相关DMRs甲基化分析显示肥胖导致的卵子甲基化异常能够部分通过雌性遗传到F1和F2卵子。这些结果说明肥胖导致的部分卵子甲基化异常能够通过雌性实现跨代遗传，这可能是代谢综合征遗传的重要原因。