Transcriptomic study of yak mammary gland tissue during lactation

Yak milk, a high-quality milk, is one of the best raw materials for dairy products and economically important to pastoral herdsmen. To make a further understanding of the molecular differences in mammary tissues of the yaks with different milk production during lactation, in this study, we took the use of RNA-seq to perform high-throughput sequencing and analysis of the mammary gland transcriptomes of both high-yielding yak and low-yielding yaks during lactation. By the comparison and analysis of the transcriptome data for the mammary gland tissue of high-yielding yak and low-yield yak, 144 differential genes were screened out, of which 49 were upregulated and 95 were downregulated. Further functional analysis indicated that these differential genes involved in multiple classes based on Gene Ontology (GO) and multiple Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The GO analysis showed that the functions of the differential genes are closely related to the carbohydrate metabolism and other biological processes. KEGG pathway analysis revealed that these genes are mostly enriched in the pathway of antigen processing and presentation, phagosome pathway and type I diabetes pathway and enriched followed by extracellular matrix receptor interaction pathway. Moreover, several other pathways related to amino acid metabolism also showed significant enrichment. Here, the mammary gland transcriptomes of high-yielding yak and low-yielding yaks during lactation have for the first time been compared, and the related differential genes have been screened out and analyzed. Our study paves a way for the further elucidation of the basic molecular mechanism of yak mammary gland tissue, and at the same time provides new ideas for improving the milk production of yaks.