Abstract
MicroRNAs are post-transcriptional regulators that play critical roles in diverse biological processes. We hypothesize that miRNAs may be involved in regulating transcriptome responses to changes in embryonic incubation temperature in chickens affecting differentiation and proliferation processes during tissue development. Therefore, we conducted comparative transcriptome profiling of miRNAs to examine altered expression in breast and hind muscle of embryos and day 35 chickens experiencing high (38.8 °C), control (37.8 °C), or low (36.8 °C) embryonic incubation temperature during embryonic day (ED) 7–10 or ED10–13. The results revealed differential expression of miRNAs due to modification of embryonic incubation temperature in a muscle type-specific and a developmental stage-specific manner. The immediate effects of thermal change observed in embryos were substantial compared to the subtle long-term effects in chickens at day 35 post-hatch. Upregulation of miR-133 in breast muscle and downregulation of miR-199a-5p, miR-1915, and miR-638 in hind muscle post ED7–10 high-temperature treatment are functionally associated with myogenesis and body size. ED10–13 low-temperature treatment led to downregulation of let-7, miR-93, and miR-130c that are related to proliferation and differentiation. The results provide insight into the dynamics of miRNA expression at variable embryonic incubation temperatures during developmental processes and indicate a major regulatory role of miRNAs in acute responses to modified environmental conditions that affect remodelling of cells and tissues.
Highlights
We found regulation of miR-222 breast and hind muscle at H10 and L13 conditions, in samples where proliferative process are important, i.e. at early in-ovo development, and that were exposed to environmental stressor, albeit physical stress not chemical stressor as in studies reviewed by Vrijems et al (2015)
For miR-199, miR-222, miR-460 we found the same direction of regulation in breast and hind muscle and/or at H10 or L13 conditions
We have demonstrated that modification of embryonic incubation temperature immediately affects miRNA expression profiles of breast and hind muscles of chicken embryos and is associated with altered expression of miRNAs in D35 chickens
Summary
We used hatching eggs from a commercial broiler line (Cobb-Vantress Inc., Siloam Springs, USA) and randomly assigned 1,001 hatching eggs to 6 experimental groups. All eggs were incubated in commercial incubators with 12 automatic turns per day (HEKA, Euro-Lux, Riet berg, Germany) at 37.8 °C with 55% relative humidity (RH) until three days prior to hatch. During the last days of incubation RH was adjusted to 65% and turning was omitted until hatching (control conditions; continuously for control groups). Broilers were slaughtered at experimental poultry abattoir of the Department of Animal Sciences (Goettingen, Germany). Breast muscle (M. pectoralis) and hind muscle (M. gastrocnemius) tissue samples were collected at the respective embryonic stages (ED10 or ED13) and at D35 post-hatch
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