Weaning Induces Stress-Dependent DNA Methylation and Transcriptional Changes in Piglet PBMCs

Abstract

Changes to the epigenome, including those to DNA methylation, have been proposed as mechanisms by which stress can induce long-term physiological changes in livestock species. Pig weaning is associated with dietary and social stress, both of which elicit an immune response and changes to the hypothalamic–pituitary–adrenal (HPA) axis. While differential methylation following stress has been assessed in model organisms, it remains poorly understood how the pig methylome is altered by stressors in production settings. We quantified changes in CpG methylation and transcript abundance in piglet peripheral blood mononuclear cells (PBMCs) following weaning and also assessed differential patterns in pigs exhibiting high and low stress response as measured by cortisol concentration and lesion scores. Blood was collected from nine gilt piglets 24 h before and after weaning, and whole-genome bisulfite sequencing (WGBS) and RNA-sequencing were performed on six and nine animals, respectively, at both time points. We identified 2,674 differentially methylated regions (DMRs) that were enriched within promoters of genes associated with lymphocyte stimulation and transcriptional regulation. Stress groups displayed unique differential methylation and expression patterns associated with activation and suppression of T cell immunity in low and high stress animals, respectively. Differential methylation was strongly associated with differential expression; specifically, upregulated genes were enriched among hypomethylated genes. We observed post-weaning hypermethylation of the glucocorticoid receptor (NR3C1) promoter and a significant decrease in NR3C1 expression (n = 9, p = 6.1 × 10–3). Our results indicate that weaning-associated stress elicits genome-wide methylation changes associated with differential gene expression, reduced T cell activation, and an altered HPA axis response.

Assessment of DNA methylation in porcine immune cells reveals novel regulatory elements associated with cell-specific gene expression and immune capacity traits

“…Many such studies have identified strong associations between cell-specific lowly methylated regions (cLMRs) and TF binding motifs as well as GWAS SNPs for relevant traits, highlighting the potential significance of these regions and of DNA methylation in regulating gene and phenotype expression [22][23][24][25][26]. DNA methylation patterns have previously been characterized in mixed porcine immune cell preparations [17,27]. However, assessment of methylation patterns in specific porcine immune cell types has not been performed, but could provide insight into transcriptional regulation and hence function relevant to pig health.…”

Asinine milk mitigates stress-mediated immune, cortisol and behavioral responses of piglets to weaning: A study to foster future interventions in humans

“…The upregulation of NR3C1 expression, as observed after weaning in piglets fed skimmed cow milk, has been noted in animals that experienced early life stress (142) and in humans diagnosed with posttraumatic stress disorder (PTSD) (143,144). However, this result contradicts the findings of studies on weanling piglets (54), that reported downregulation of NR3C1 expression in contrast to high levels of circulating cortisol.…”

“…Modulation of the immune system has lifelong consequences and may be studied through molecular biology assays, which are tools to explore gene expression levels and regulation methods (51). Recently, studies have focused on the abundance of mRNAs from peripheral blood mononuclear cells (PBMCs) (52) isolated from immune cells in whole blood (53), to assess gene expression changes in response to adverse stimuli associated with stressful events (54,55).…”

Improving hydrocarbon toxicity tolerance in poultry: role of genes and antioxidants

“…There are therefore heritable alterations in gene expression that do not necessitate any change in the DNA sequence ( Jirtle and Skinner, 2007 ; Guerrero-Bosagna and Skinner, 2012 ). Epigenetic processes influence the ability of an organism to adjust to prevailing environmental perturbance and include DNA methylation, histone acetylation, and non-coding ribonucleic acids ( Ju et al, 2020 ; Corbett et al, 2021 ). These modifications are classical epigenetic mechanisms involved in packaging the chromatin structure, regulating DNA damage, and repressing gene expression, among other transcriptional activities ( Bannister and Kouzarides, 2011 ; Hunt et al, 2013 ).…”