Putative Epigenetic Biomarkers of Stress in Red Blood Cells of Chickens Reared Across Different Biomes

• Production animals are constantly subjected to early adverse environmental conditionsthat influence the adult phenotype and produce epigenetic effects. CpG dinucleotidemethylation in red blood cells (RBC) could be a useful epigenetic biomarker to identifyanimals subjected to chronic stress in the production environment. Here we compareda reduced fraction of the RBC methylome of chickens exposed to social isolation tonon-exposed. These experiments were performed in two different locations: Brazil andSweden. The aim was to identify stress-associated DNA methylation profiles in RBC across these populations, in spite of the variable conditions to which birds are exposedin each facility and their different lineages. Birds were increasingly exposed to a socialisolation treatment, combined with food and water deprivation, at random periods of theday from weeks 1–4 after hatching. We then collected the RBC DNA from individualsand compared a reduced fraction of their methylome between the experimental groupsusing two bioinformatic approaches to identify differentially methylated regions (DMRs):one using fixed-size windows and another that preselected differential peaks with MACS2. Three levels of significance were used (P ≤ 0.05, P ≤ 0.005, and P ≤ 0.0005) to identify DMRs between experimental groups, which were then used for differentanalyses. With both of the approaches more DMRs reached the defined significancethresholds in BR individuals compared to SW. However, more DMRs had higher foldchange values in SW compared to BR individuals. Interestingly, ChrZ was enrichedabove expectancy for the presence of DMRs. Additionally, when analyzing the locationsof these DMRs in relation to the transcription starting site (TSS), we found threepeaks with high DMR presence: 10 kb upstream, the TSS itself, and 20–40 kbdownstream. Interestingly, these peaks had DMRs with a high presence (>50%) ofspecific transcription factor binding sites. Three overlapping DMRs were found betweenthe BR and SW population using the most relaxed p-value (P ≤ 0.05). With the most stringent p-value (P ≤ 0.0005), we found 7 and 4 DMRs between treatmentsin the BR and SW populations, respectively. This study is the first approximation toidentify epigenetic biomarkers of long-term exposure to stress in different lineages ofproduction animals.

Subject headings

NATURVETENSKAP  -- Biologi -- Genetik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Genetics (hsv//eng)

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

Keyword

stress

red blood cells

epigenetics

chicken

DNA methylation

animal welfare

Publication and Content Type

ref (subject category)

art (subject category)