Association of DNA methylation levels with tissue-specific expression of adipogenic and lipogenic genes in Longissimus dorsi muscle of Korean cattle

Abstract Text: The epigenetic factor such as DNA methylation status may regulate adipogenesis and lipogenesis, affecting intramuscular fat (IMF) deposition of longissimus dorsi muscle (LM) in beef cattle. In steers, the LM consists mainly of muscle tissue. However, the LM in Korean cattle steers also contains IMF. We compared the gene expression levels between the IMF and muscle portions of the LM steers after separation of the tissues. Real-time PCR analysis showed that mRNA levels of both adipogenic peroxisome proliferator- activated receptor gamma isoform 1 (PPARγ1) and lipogenic fatty acid binding protein 4 (FABP4) were higher (P <0.01) in the IMF portion than in the muscle portion of the LM. DNA methylation at specific sites within regulatory regions of gene is known to regulate transcription. We determined DNA methylation levels of regulatory regions of the PPAR γ1 and  FABP4 genes by pyrosequencing of genomic DNA isolated from the IMF and muscle portions of the LM.  DNA methylation levels of two CpG sites out of three from regulatory region (+144 ~ +225) of  PPARγ1 gene were lower (P < 0.05) in the IMF portion than in muscle portion of the LM. DNA methylation levels of all five CpG sites from regulatory regions (-9664 ~ -9469) of FABP4 gene were also lower (P< 0.001) in IMF portion than in the muscle portion. Thus, mRNA levels of both PPARγ1 and FABP4 genes were inversely correlated with DNA methylation levels of regulatory regions of CpG sites of the corresponding gene. In conclusion, our findings suggest that DNA methylation status regulates tissue-specific expression of adipogenic and lipogenic gene expression in IMF and muscle portions of LM tissues of Korean cattle steers.

Keywords: Intramuscular fat, adipogenesis, DNA methylation