DNA Methylation of Postnatal Liver Development in Pigs

DNA methylation plays an important role in the development and tissue differentiation of eukaryotes. In this study, bisulfite sequencing (BS-seq) technology was used to analyze the DNA methylation profiles of liver tissues taken from Rongchang pigs at three postnatal feeding stages, including newborn, suckling, and adult. The DNA methylation pattern across the genomes or genic region showed little difference between the three stages. We observed 419 differentially methylated regions (DMRs) in promoters, corresponding to 323 genes between newborn and suckling stages, in addition to 288 DMRs, corresponding to 134 genes, between suckling and adult stages and 351 DMRs, corresponding to 293 genes, between newborn and adult stages. These genes with DMRs were mainly enriched in metabolic, immune-related functional processes. Correlation analysis showed that the methylation level of gene promoters was significantly negatively correlated with gene expression. Further, we found that genes related to nutritional metabolism, e.g., carbohydrate metabolism (FAHD1 and GUSB) or fatty acid metabolism (LPIN1 and ACOX2), lost DNA methylation in their promoter, with mRNA expression increased in newborn pigs compared with those in the suckling stage. A few fatty acid metabolism-related genes (SLC27A5, ACOX2) were hypomethylated and highly expressed in the newborn stage, which might satisfy the nutritional requirements of Rongchang pigs with high neonatal birth rates. In the adult stage, HMGCS2-which is related to fatty acid β-oxidation-was hypomethylated and highly expressed, which explains that the characteristics of high energy utilization in adult Rongchang pigs and their immune-related genes (CD68, STAT2) may be related to the establishment of liver immunity. This study provides a comprehensive analysis of genome-wide DNA methylation patterns in pig liver postnatal development and growth. Our findings will serve as a valuable resource in hepatic metabolic studies and the agricultural food industry.