Association of DNA Methylation Levels with Tissue-specific Expression of Adipogenic and Lipogenic Genes in Longissimus dorsi Muscle of Korean Cattle

Epigenetic factors, such as DNA methylation status, may regulate adipogenesis and lipogenesis, thus affecting intramuscular fat (IMF) deposition in longissimus dorsi muscle (LM) of beef cattle. In Korean cattle steers, the LM consists mainly of muscle tissue. However, the LM tissue also contains IMF. We compared the gene expression levels between the IMF and muscle portions of the LM after tissue separation. Real-time polymerase chain reaction analysis showed that the mRNA levels of both adipogenic peroxisome proliferator-activated receptor gamma isoform 1 (PPARG1) and lipogenic fatty acid binding protein 4 (FABP4) were higher (p<0.01) in the IMF than in the muscle portion of the LM. We determined DNA methylation levels of regulatory regions of the PPARG1 and FABP4 genes by pyrosequencing of genomic DNA. DNA methylation levels of two of three CpG sites in the PPARG1 gene promoter region were lower (p<0.05) in the IMF than in the muscle portion of the LM. DNA methylation levels of all five CpG sites from the FABP4 gene promoter region were also lower (p<0.001) in the IMF than in the muscle portion. Thus, mRNA levels of both PPARG1 and FABP4 genes were inversely correlated with DNA methylation levels in regulatory regions of CpG sites of the corresponding gene. Our findings suggest that DNA methylation status regulates tissue-specific expression of adipogenic and lipogenic genes in the IMF and muscle portions of LM tissue in Korean cattle.