Determination and Difference Analysis of DNA Methylation Content Both in Blood and Muscle Tissue of Pigs

In this experiment, DNA samples from parental lines Large White, Landrace, and Meishan pigs, and their hybrids Large White × Landrace, Landrace × Large White, Large White × Meishan, and Meishan × Large White pigs were used for the determination of DNA methylation content in both blood and muscle tissue. The differences about DNA methylation content between parental lines and their hybrids were analyzed. These will offer theoretical support from molecular level for heterosis. High performance liquid chromatography (HPLC) was firstly used to detect DNA methylation content. The average DNA methylation content in 163 DNA samples of muscle tissue was 16.92%, whereas, the average DNA methylation content in 182 samples of blood was 6.49%, the difference between which was especially prominent (P < 0.01). In blood, the methylation content was lower than 10%, with the highest level of 9.93% in Landrace × Large White and the lowest of 2.97% in Landrace. The difference between Large White and Landrace was highly significant (P < 0.01), but not significant between Large White and Meishan; and the differences between reciprocal cross hybrids in both hybrid systems were significant (P < 0.05). In muscle tissue, the differences in methylation content among three parents were not significant (P > 0.05); and the differences between reciprocal cross hybrids in both hybrid systems were not significant (P > 0.05), but between different hybrid systems, the hybrids had a significant difference (P < 0.05). The average methylation content in muscle samples was higher than that in blood samples, and the methylation in different tissues was different.