Short communication: Locus-specific interrelations between gene expression and DNA methylation patterns in bovine mammary gland infected by coagulase-positive and coagulase-negative staphylococci.

Pathogens are able to alter the cell cycle program and immune response of the host by changing the transcription and epigenetics of genes responsible for cell cycle control and inflammation. In this regard, we evaluated interrelations between DNA methylation and expression of autophagy, apoptosis, and lipid metabolism-related genes in a sample set of mammary gland secretory tissue sections derived from bovine mammary glands infected with coagulase-negative and coagulase-positive staphylococci. We assessed relative transcript abundance and DNA bisulfite sequencing in loci of the ATG5, IGF1R, TERT, and DGAT1 genes. Lack of DNA methylation in ATG5 and DGAT1 loci might be associated with maintenance of ATG5 and DGAT1 expression regardless of the health status of bovine mammary gland. Complete methylation of intragenic CpG regions in the IGF1R locus was apparently not related to the presence of its transcript in the investigated udder parenchyma samples. Detected hypermethylation of the TERT upstream element was associated with a small amount of TERT mRNA in bovine mammary gland, regardless of the presence, or absence, of the pathogen. A significant decrease in TERT gene expression in tissue sections of mammary gland free of bacteria and in those infected with coagulase-positive staphylococci was observed in parenchyma samples infected with coagulase-negative staphylococci. Two possible explanations are the direct involvement of the TERT gene in the etiology of bovine mastitis or the increase of TERT mRNA due to activation of the MAPK signaling pathway in response to release of exotoxins by coagulase-negative bacteria in the bovine mammary gland.