mRNA Expressions of Methylation Related Enzymes and Duration of Thermal Conditioning in Chicks

DNA methylation regulates gene expression by modifying the nucleosome structure of DNA, without altering the gene sequence. It has been reported that DNA methylation reactions are catalyzed by several enzymes. In chickens, thermal conditioning treatment affects the central DNA methylation levels. The purpose of this study was to clarify the changes in DNA methylation and demethylation factors during thermal conditioning in the hypothalamus of 3-dayold chicks. Male chicks (3-days old) were exposed to 40±0.5℃ as a thermal conditioning treatment for 1, 2, 6, 9, or 12 h. The control chicks were kept in a thermoneutral zone (30±0.2℃). After thermal conditioning, the mRNA levels ofDNA methyltransferase (DNMT)-1,-3a,-3b, and ten-eleven translocation (TET)-1,-2, and-3 in the hypothalamus were measured by q-PCR. The mRNA levels ofDNMT-3a and TET-1 were increased by thermal conditioning. Moreover, the expression level ofTET-1 increased with the loading time ofthe thermal conditioning. The gene expressions of DNMT-1, DNMT-3b, TET-2, and TET-3 were not affected by thermal conditioning. Since DNMT-3a is a catalyst for de-novo DNA methylation and TET-1 catalyzes the oxidation ofmethylated cytosine, it is suggested that the thermal conditioning increased the activation ofDNA methylation and demethylation factors, which occur in the hypothalamus ofneonatal chicks.