| dc.description.abstract | Stress-induced epigenetic modifications and the accompanying shifts in gene expression could be a potential mechanism behind the performance differences seen in prenatally stressed offspring. Two groups of cows were used to investigate the impact of prenatal transportation stress on DNA methylation patterns in Brahman females. One group was transported 5 times for 2-hour periods every 20-day starting from day 60 of gestation, while the other was maintained as a non-transport group. At 28 days old, blood was collected from heifer calves born from the two groups. At 5 years of age, cows were slaughtered, and the adrenal cortex, adrenal medulla, anterior pituitary, paraventricular nucleus of the hypothalamus, and amygdala were harvested from each cow. Ultimately 6 females born from the transport group (PNS) and 8 females born from the non-transport group (Control) were used to obtain methylation data.
In the DNA from leukocytes, 16,377 cytosine-guanine sites were differentially methylated in PNS females compared to the Control cows. Some differentially methylated sites were located within promoter regions of genes involved in important biological pathways. In amygdala tissue harvested at 5 years, there were only 29 differentially methylated sites between the PNS and the Control. Analysis of the overall methylation of specific genomic features (including genes) revealed 134 differentially methylated promoter regions, 202 gene bodies, and 133 cytosine-phosphate-guanine islands. Only 2 genes were differentially expressed between the two groups: The solute carrier family 28 member 3 and Fc fragment of IgG receptor IIa. Neither gene had any differentially methylated regions associated with them. Inter-individual variability of DNA methylation was the greatest in the anterior pituitary gland for both groups, followed by the leukocytes and the amygdala with the least. There was minimal overlap of variably methylated genomic regions between tissues and treatment groups.
There were extensive differences in DNA methylation patterns from leukocytes harvested at 28 days in the prenatally stressed heifer calves relative to the control. However, at 5 years of age, the two groups had minimal differences in methylation patterns. The interindividual variation observed appears to be tissue specific. An interaction between the prenatal environment and cow genotype could be responsible for the differences in locations of variably methylated regions between the PNS and Control animals. | |
