本研究基于20头成华猪和30头青裕猪的简化代表性甲基化测序数据使用全基因组分析的方法识别成华猪和青裕猪差异甲基化位点。当甲基化位点的甲基化差异大于0.25以及q值小于0.01时，把该位点识别为差异甲基化位点，然后基于差异甲基化位点搜索对应的差异甲基化基因。结果发现成华猪的几个肉质性状，包括45分钟的pH值 (pH_45min)，45分钟的肉色亮度值（L45_min）以及24小时的肉色亮度值（L_24h），均显著高于青裕猪。然后我们检测到10699个差异甲基化位点，并基于这些位点搜索到2760个差异甲基化基因。通过基因功能分析我们发现这些差异甲基化基因主要涉及AMPK信号通路，II型糖尿病，胰岛素信号通路，mTOR信号通路以及胰岛素抵抗等。此外，通过相关文献和研究资料，发现一些差异甲基化基因与脂质代谢，肌肉发育以及肉质性状相关。本研究结果表明成华猪和青裕猪有着不同的甲基化模式，这些甲基化模式的差异反映了二者表型性状的差异。本研究基于简化甲基化测序数据对成华猪和青裕猪进行全基因组甲基化差异分析，研究结果系统解析了成华猪和青裕猪的DNA甲基化模式和表观遗传调控机制。

To develop a modified live vaccine (MLV) against porcine reproductive and respiratory syndrome virus (PRRSV), virulent CH-1a strain was attenuated by serial passages up to 130 passage (P130) in Marc-145 cells. The virulence and immune efficacy of the attenuated CH-1a were evaluated in pigs. The results showed that animals inoculated with P130 did not develop any clinical sign of the disease, but produced rapid and effective humoral immune responses against PRRSV challenge, indicating that attenuated CH-1a P130 is the candidate as the effective vaccine against PRRSV. To define the potential mutations in the attenuated CH-1a genome, we sequenced and analyzed the ORF5 gene of CH-1a strain of different passages (P39, P55, P65, P70, P85, P100, P115, P120, P125, and P130) and found that three mutations (C5Y, H38Q and L146Q) which may be related with the attenuation of CH-1a. In addition, we also found a unique restriction enzyme site (TspEI) in the ORF5 gene of attenuated CH-1a, which can be used as a genetic marker to distinguish original and attenuated CH-1a.