Crucial genes at the onset of lactation revealed by transcriptome screening of Domestic Yak mammary gland

At the onset of lactation, there are three distinct stages of mammary tissue development and function including mammogenesis, colostrogenesis, and lactogenesis. The mechanism of the transition from colostrogenesis to lactogenesis of Maiwa Yak is still unknown. In this study, mammary tissues from three Maiwa Yaks were collected at 1 and 30 d after parturition for transcriptome exploration using Affymetrix Bovine Genome Arrays. Comparing 1 and 30 d results, a total of 517 annotated differentially expressed genes (DEGs) were identified at the criteria of a P ≤ 0.05. The ratio of up-regulated genes to the down-regulated ones was around 1:2 (more specifically, 164:353). To depict the profile of DEGs, a dynamic impact approach (DIA) was used to analyse the microarray data based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. GO terms “fatty acid transport” and “monocarboxylic acid transport” were significantly induced during the colostrum period. The strongly impacted KEGG pathways were “chondroitin sulfate biosynthesis”, “glycosphingolipid biosynthesis”, and “glycerolipid metabolism”. These data may provide candidate genes with a high probability of having functional roles in regulating the transition from colostrum to normal milk in domestic yak mammary gland.