Tibetan pigs live between 2500 and 4300 m above sea level on the Tibetan Plateau, and are better adapted to
hypoxia than lowland pigs.
MicroRNAs (
miRNAs) are involved in a wide variety of cellular processes; however, their regulatory role in
hypoxia adaptation remains unclear. In this study,
miRNA-seq was used to identify differentially expressed
miRNAs (DE
miRNAs) in the cardiac muscle of Tibetan and Yorkshire pigs, which were both raised in high elevation environments. We obtained 108 M clean reads and 372 unique
miRNAs, which included 210 known porcine
miRNAs, 136 conserved in other mammals, and 26 novel pre-
miRNAs. In addition, 20 DE
miRNAs, including 10 up-regulated and 10 down-regulated
miRNAs, were also found after comparison between Tibetan and Yorkshire pigs. We predicted
miRNA targets based on differential expression and abundance in the two populations. Furthermore, the results of a Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that DE
miRNAs in Tibetan and Yorkshire pigs are involved in
hypoxia-related signaling pathways such as the
mitogen-activated protein kinase, which is the mechanistic target of
rapamycin, and the
vascular endothelial growth factor, as well as
cancer-related signaling pathways. Five DE
miRNAs were randomly selected to validate the results of
miRNA-seq using real-time polymerase chain reaction, and the results corresponded to those from the
miRNA-seq, confirming that deep-sequencing methods are feasible and efficient. In our study, we identified various previously unknown
hypoxia-related
miRNAs in pigs, and the data obtained suggest that
hypoxia-related
miRNA expression patterns are significantly altered in the Tibetan pig compared to other species. Therefore, DE
miRNAs may play an important role in organisms that have adapted to hypoxic environments.