Identification and characterization of microRNAs in the liver of yak (Bos grunniens) associated with energy deficiency at high-altitude.

Abstract

Objective: MicroRNAs (miRNAs) are small non-coding RNAs that regulate various biological processes including systemic metabolism and energy homeostasis. Comprehending hepatic functional adaptations is critical for yak (Bos grunniens) cattle as these herds typically suffer from malnutrition during the most of winter grazing seasons.

Methods: To enhance the understanding of miRNA mediated post-transcriptional regulation in the context of energy deficiency in yaks, the miRNA transcriptomes of liver were profiled using deep sequencing analyses.

Results: A total of 17,562,643 clean reads were acquired from a liver library, resulting in the identification of 369 known and 41 novel miRNA candidates. The top 10 miRNAs accounted for greater than 92% (9,854,350 counts) of the miRNAome, which were predicted to target 2,333 genes. Among the highly expressed miRNAs, miR-122 accounts for 57%, followed by bta-let-7f and bta-let-7a-5p. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses using DAVID bioinformatics resources indicated that the identified miRNAs targeted genes enriched in transcription and metabolism processes. Notably, 11 of the top 20 miRNAs were predicted to play a role in the regulation of lipid as well as glucose homeostasis via the PI3K-Akt interaction network.

Conclusion: This is the first, at the best of our knowledge, liver miRNA-seq profiling analysis of moderate yak cows subjected to the combined effects of cold and nutritional stress at high altitude. Tissue specific miR-122 and liver enriched bta-let-7f represent two of the most abundant miRNAs found in the liver of yak cows. These findings enhance our understanding of the role of hepatic miRNAs in energy deficiency in yaks during winter grazing at high altitudes.