Cardiac and Skeletal Muscle Transcriptome Response to Heat Stress in Kenyan Chicken Ecotypes Adapted to Low and High Altitudes Reveal Differences in Thermal Tolerance and Stress Response

Abstract

Heat stress (HS) negatively affects chicken performance. Agricultural expansion will happen in regions that experience high ambient temperatures, where fast-growing commercial chickens are vulnerable. Indigenous chickens of such regions, due to generations of exposure to environmental challenges, might have higher thermal tolerance. In this study, two indigenous chicken ecotypes, from the hot and humid Mombasa (lowland) and the colder Naivasha (highland) regions, were used to investigate the effects of acute (5 h, 35°C) and chronic (3 days of 35°C for 8 h/day) HS on the cardiac and skeletal muscle, through RNA sequencing. The rectal temperature gain and the number of differentially expressed genes (DEGs) [False Discovery Rate (FDR) < 0.05] were two times higher in the acute stage than in the chronic stage in both ecotypes, suggesting that cyclic exposure to HS can lead to adaptation. A tissue- and stage-specific difference in response to HS was observed, with peroxisome proliferator-activated-receptor (PPAR) signaling and mitogen-activate protein kinase (MAPK) signaling pathways, enriched in heart and skeletal muscle, respectively, and the p53 pathway enriched only in the acute stage in both tissues. The acute and chronic stage DEGs were integrated by a region-specific gene coexpression network (GCN), and genes with the highest number of connections (hub genes) were identified. The hub genes in the lowland network were CCNB2, Crb2, CHST9, SESN1, and NR4A3, while COMMD4, TTC32, H1F0, ACYP1, and RPS28 were the hub genes in the highland network. Pathway analysis of genes in the GCN showed that p53 and PPAR signaling pathways were enriched in both low and highland networks, while MAPK signaling and protein processing in endoplasmic reticulum were enriched only in the gene network of highland chickens. This shows that to dissipate the accumulated heat, to reduce heat induced apoptosis, and to promote DNA damage repair, the ecotypes activated or suppressed different genes, indicating the differences in thermal tolerance and HS response mechanisms between the ecotypes. This study provides information on the HS response of chickens, adapted to two different agro climatic environments, extending our understanding of the mechanisms of HS response and the effect of adaptation in counteracting HS.

Emerging Genetic Tools to Investigate Molecular Pathways Related to Heat Stress in Chickens: A Review

“…A study in support of the central role of HSPs in facing HS is the recent research of Srikanth et al Using RNA-Seq methods (in liver and heart tissues), two indigenous chicken ecotypes from Kenya were compared; the animals were sampled from the tropical climate in Mombasa (lowland) and the colder Naivasha (highland) regions in order to investigate the effects of acute (5 h, 35 °C) and chronic (3 days of 35 °C for 8 h/day) HS. Only four different differentially expressed genes (DEGs) were found in all four experimental groups and were identified as HSP70 family member 8 (HSPA8) both in acute and chronic HS and small HSP family member 7 (HSPB7) in acute HS [ 129 ]. Moreover, Fatty Acid–Binding Protein 4 ( FABP4 ) was found differentially expressed in chronic HS [ 129 ] and also in the hypothalamus of a broiler chicken [ 130 ].…”

“…Only four different differentially expressed genes (DEGs) were found in all four experimental groups and were identified as HSP70 family member 8 (HSPA8) both in acute and chronic HS and small HSP family member 7 (HSPB7) in acute HS [ 129 ]. Moreover, Fatty Acid–Binding Protein 4 ( FABP4 ) was found differentially expressed in chronic HS [ 129 ] and also in the hypothalamus of a broiler chicken [ 130 ]. The FABP4 gene is involved in the Peroxisome Proliferator-Activated Receptor ( PPAR ) signaling pathway, which is required for energy metabolism and regulating the oxidative stress-induced inflammatory response [ 129 , 131 ].…”

Genome-Wide Transcriptome and Metabolome Analyses Provide Novel Insights and Suggest a Sex-Specific Response to Heat Stress in Pigs

“…The processing of the data was previously described [25]. Briefly, after checking the quality of the raw reads using FastQC (version 0.11.5) [26] and trimming the adaptors and low-quality bases using TRIMMOMATIC (version 0.36) [27], the reads were aligned to the Pig reference genome (Sus scrofa 11.1) using HiSAT2 (version 2.05) [28].…”

Transcriptome of Chicken Liver Tissues Reveals the Candidate Genes and Pathways Responsible for Adaptation into Two Different Climatic Conditions

“…Liver tissues are not only comprised of hepatocytes cells but also composed of many blood and immune cells [7]. Several studies reported that multiple pathways such as gluconeogenesis, fatty acids metabolism, PPAR pathways are differentially regulated during adaptation [5,[8][9][10]. Identification of such pathways and genes involved in adaptation to two different environmental conditions may help in elucidation of the molecular mechanism behind such adaptation [11].…”