Epigenetic DNA methylation in the promoters of Peroxisome Proliferator-Activated Receptor γ in chicken lines divergently selected for fatness

Peroxisome proliferator-activated receptor. is a master regulator of adipocyte differentiation and function gamma Expression of PPAR gamma in mammals is regulated by DNA methylation; however, it is currently unknown whether chicken PPAR gamma expression is regulated by DNA methylation. To enhance our understanding of molecular mechanisms underlying chicken adipose tissue development and adipogenesis, we investigated the promoter methylation status and gene expression of PPAR gamma gene in Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF). Deoxyribonucleic acid methylation was analyzed by bisulfite sequencing method, and mRNA expression was detected by real-time quantitative real time reverse-transcription polymerase chain reaction (RT-PCR). The analyzed region located from -1,175 to -301 bp upstream of the translation start codon ATG contains 6 CpG dinucleotides, which are located at positions -1,014, -796, -625, -548, -435, and -383 bp, respectively. The results revealed that the 3 CpGs at positions -548, -435, and -383 bp showed differential methylation between the lean and fat chicken lines, but the other 3 CpG sites at positions -1,014, -796, and -625 bp did not. PPAR gamma gene promoter methylation in both chicken lines decreased with age, and PPAR gamma promoter methylation levels were significantly higher in lean than fat broilers at 2 wk of age (79.9 to 64.5%; P < 0.0001), at 3 wk of age (66.7 to 58.3%; P < 0.0001), and at 7 wk of age (50.0 to 42.7%; P = 0.0004). Real-time quantitative RT-PCR analysis showed that, negatively correlated with DNA methylation (Pearson's r = -0.653, P = 0.0057), PPAR gamma expression was increased with age and significantly lower in lean than fat chicken lines at 2, 3, and 7 wk of age (P < 0.0001). In conclusion, our findings suggest that chicken PPAR gamma is regulated by DNA methylation during adipose tissue development.