Comparative Expression Analysis of Heat-Adaptation Candidate Genes in some Thermoregulatory Tissues of Temperate and Tropical Cattle

Skin is one of the thermoregulatory organs that ensures homeothermy, a critical function for animal adaptation to hot and cold environments. It is the most exposed thermoregulatory organ that interfaces with the environment. In a previous study, we evaluated heat stress genes in various thermoregulatory organs [skin, kidney, heart, brain (hypothalamus), and adrenal glands] obtained from African Bos indicus (White Fulani, Sokoto Gudali) and African Bos taurus (Muturu, N'dama) compared to representative taurine and indicus cattle in the USA (Angus, Brahman) to quantify gene differential expression. We identified 225 differentially expressed genes. In this study, we sought to validate and quantify differential expression of mRNA from six genes identified in the previous RNA-seq profiling. We utilized quantitative PCR (qPCR) to profile CES1, CSN2, TDO2, ALOX12E, SYT4 and RPS23 genes, obtained from tissues derived from tropical (White Fulani, WF) and temperate (Angus, AG) cattle. A total of 12 animals, representative of the breeds were included in the study. Four genes, previously found to be significantly up-regulated, were similarly highly upregulated in WF: CES1 had a 144.19-fold change, SYT4 a 106.29-fold change, CSN2 a 100.89-fold change, and TD02 a 54.78-fold change. The SYT4 gene which was previously reported as down-regulated, was found to be significantly up-regulated in WF and down-regulated in AG. Additionally, CES1, CSN2, TDO2 and ALOX12E were all down-regulated in AG, with similar mRNA expression as reported in our previous study. The results from these two studies are highly consistent and our current results validate results obtained in our earlier RNA-seq study. These results suggest that bovine skin thermoregulation plays a significant role in heat adaptation.