Transient Shifts of Incubation Temperature Reveal Immediate and Long-Term Transcriptional Response in Chicken Breast Muscle Underpinning Resilience and Phenotypic Plasticity

Abstract

Variations in egg incubation temperatures can have acute or long-term effects on gene transcription in avian species. Altered gene expression may, in turn, affect muscle traits in poultry and indirectly influence commercial production. To determine how changes in eggshell temperature affect gene expression, incubation temperatures were varied [36.8°C (low), 37.8°C (control), 38.8°C (high)] at specific time periods reflecting two stages of myogenesis [embryonic days (ED) 7–10 and 10–13]. Gene expression was compared between interventions and matching controls by microarrays in broiler breast muscle at ED10 or ED13 and post-hatch at day 35. Early (ED7-10) high incubation temperature (H10ΔC) resulted in 1370 differentially expressed genes (DEGs) in embryos. Ingenuity pathway analysis revealed temporary activation of cell maintenance, organismal development, and survival ability genes, but these effects were not maintained in adults. Late high incubation temperature (ED10-13) (H13ΔC) had slightly negative impacts on development of cellular components in embryos, but a cumulative effect was observed in adults, in which tissue development and nutrition metabolism were affected. Early low incubation temperature (L10ΔC) produced 368 DEGs, most of which were down-regulated and involved in differentiation and formation of muscle cells. In adults, this treatment down-regulated pathways of transcriptional processes, but up-regulated cell proliferation. Late low temperature incubation (L13ΔC) produced 795 DEGs in embryos, and activated organismal survival and post-transcriptional regulation pathways. In adults this treatment activated cellular and organ development, nutrition and small molecule activity, and survival rate, but deactivated size of body and muscle cells. Thermal interventions during incubation initiate immediate and delayed transcriptional responses that are specific for timing and direction of treatment. Interestingly, the transcriptional response to transiently decreased incubation temperature, which did not affect the phenotypes, prompts compensatory effects reflecting resilience. In contrast, higher incubation temperature triggers gene expression and has long-term effects on the phenotype. These mechanisms of considerable phenotypic plasticity contribute to the biodiversity and broaden the basis for managing poultry populations.

miRNAs regulate acute transcriptional changes in broiler embryos in response to modification of incubation temperature

“…Integrating miRNA expression data with previous gene expression profiles of matched samples ( www.ncbi.nlm.nih.gov/geo ; accession number: GSE76670) using correlation analysis revealed “functional” miRNAs with negatively correlated miRNA–mRNA relationships. From our previous study, we found that increasing temperature from 37.8 °C to 38.8 °C during ED7–10 (H10) and decreasing temperature from 37.8 °C to 36.8 °C during ED10–13 (L13) resulted in considerable immediate transcriptomic changes (based on the abundance of differentially expressed genes) in embryos, whereas decreasing temperature during ED7–10 (L10) as well as ED10–13 (L13) showed large long-term effects in D35 chickens 4 , 5 . Therefore, we focused on these treatment conditions that showed most prominent changes of the mRNA expression.…”

“…For functional analysis, we focused on those thermal treatment conditions ((H10) and (L13) in embryos (L10) and (L13) in D35 chickens) that were previously found to show the most prominent mRNA-transcript changes 4 , 5 . Pairs of miRNAs and mRNAs were identified by in-silico target prediction complemented by experimental evidence based on the correlation analysis of miRNA and mRNA expression data obtained from identical samples.…”

“…To identify functional miRNAs and potential target genes, we integrated miRNA expression data from the present study and mRNA expression data of samples from our previous publications 4 , 5 using correlation analysis and target prediction (Fig. 1 ).…”

“…Our previous experiments showed acute and long-term transcriptomic changes with temperature manipulation during muscle fibre formation. Thermal incubation treatments influence several biological functions and pathways depending on stage of muscle fibre development 4 , 5 . Hence, manipulation of embryonic incubation temperature may have implications in broiler meat production.…”

The Role of Incubation Conditions in the Onset of Avian Myopathies

“…Significant adverse effects on meat yield and muscle development have been observed with continuous or long-term (more than 6 h) cyclic high temperatures (>38°C) during incubation ( Hulet et al, 2007 ; Naraballobh et al, 2016a , b ; Clark et al, 2017 ). High incubation temperatures increase oxygen consumption of embryos during the late endothermic phase of incubation that occurs in the 3 to 4 days before hatch ( Janke et al, 2002 ; Mortola and Labbè, 2005 ; Molenaar et al, 2010 , 2013 ).…”