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DNA methylation is a possible basis of phenotypic alterations observed in suckling Brahman calves
The objective of this experiment was to examine DNA methylation as a potential basis for phenotypic alterations observed in prenatally stressed (PNS) compared to control calves (Littlejohn et al., 2016). Previously, 41 of 85 mature Brahman cows were transported for 2-h periods at 60, 80, 100, 120, and 140 d of gestation, while the remaining cows were controls (n=44). All calves born to control and transported dams (PNS group) were evaluated to determine phenotypic differences in temperament, circulating concentrations of cortisol, immune function, and metabolism as suckling calves. At 28 d of age each calf was restrained for collection of jugular blood samples. Buffy coat cells were harvested from whole blood and stored at -80 C. DNA was isolated from buffy coat cells of 7 PNS and 7 control bulls using phenol-chloroform extraction procedures and the samples were analyzed using reduced representation bisulfite sequencing (Zymo Research; Irvine, CA) to determine differential methylation of DNA. Reported genes were differentially methylated (P < 0.015) in PNS compared to control calves (Table 1). Genes that were defined as strongly hypermethylated (n=41) were ≥33% more methylated in PNS than control bulls, while genes that were defined as strongly hypomethylated (n=49) were ≥33% less methylated than controls. Reported genes were related to immune function, metabolic function, behavior/stress/neural function, reproductive function, and cell signaling/gene function. Several genes were ascribed to multiple functions. Differentially methylated genes related to phenotypic alterations observed in PNS compared to control bull calves suggest epigenetic programming of biological systems in utero.
Keywords:
calves, DNA methylation, prenatal stress