Transcriptomic profiles of the bovine mammary gland during lactation and the dry period

Abstract

The initiation and maintenance of lactation are complex phenomena governed by biochemical and endocrine processes in the mammary gland (MG). Although DNA-based approaches have been used to study the onset of lactation, more comprehensive RNA-based techniques may be critical in furthering our understanding of gene alterations that occur to support lactation in the bovine MG. To further determine how gene profiles vary during lactation compared with the dry period, RNA-seq transcriptomic analysis was used to identify differentially expressed genes (DEG) in bovine MG tissues from animals that were lactating and not lactating. A total of 881 DEG (605 upregulated and 276 downregulated) were identified in MG of 3 lactating Chinese Holstein dairy cows versus the 3 dry cows. The subcellular analysis showed that the upregulated genes were most abundantly located in "integral to membrane" and "mitochondrion," and the top number of downregulated genes existed in "nucleus" and "cytoplasm." The functional analysis indicated that the DEG were primarily associated with the support of lactation processes. The genes in higher abundance were most related to "metabolic process," "oxidation-reduction process," "transport" and "signal transduction," protein synthesis-related processes (transcription, translation, protein modifications), and some MG growth-associated processes (cell proliferation/cycle/apoptosis). The downregulated genes were mainly involved in immune-related processes (inflammatory/immune/defense responses). The KEGG analysis suggested that protein synthesis-related pathways (such as protein digestion and absorption; protein processing in endoplasmic reticulum; and glycine, serine, and threonine metabolism) were highly and significantly enriched in the bovine MG of lactating cows compared to dry cows. The results suggested that the dry cows had decreased capacity for protein synthesis, energy generation, and cell growth but enhanced immune response. Collectively, this reduced capacity in dry cows supports the physiological demands of the next lactation and the coordinated metabolic changes that occur to support these demands. A total of 51 identified DEG were validated by RT-PCR, and consistent results were found between RT-PCR and the transcriptomic analysis. This work provides a profile of gene-associated changes that occur during lactation and can be used to facilitate further investigation of the mechanisms underlying lactation in dairy cows.

Seryl-tRNA synthetase-mediated essential amino acids regulate β-casein synthesis via cell proliferation and mammalian target of rapamycin (mTOR) signaling pathway in bovine mammary epithelial cells

“…To date, potential functional roles of AARS involved in AA regulating milk protein synthesis have been identified in humans (Han et al, 2012) and dairy cows (Wang et al, 2014). Furthermore, SARS has been shown to be closely related to lactation in dairy cows that were fed different roughages (Dai et al, 2017a) or during varying lactation periods (Dai et al, 2017b(Dai et al, , 2018. Therefore, the present find- Figure 3.…”

Identification of regulatory networks and hub genes controlling mammary gland development and lactation in dairy goats during the late lactation, dry period, and late gestation stages

“…In this study, RNA-Seq and bioinformatics analysis were performed on the mammary gland tissues of dairy goats in the LL, DP, and LG stages, and the gene expression pro les related to mammary gland development and lactation were mapped to construct mammary gland growth, proliferation, apoptosis, immunity, substance transport, synthesis, and metabolic-related networks. Prior to this study, studies have reported the transcriptome analysis of mammary gland tissues during the lactating and DP stages in pigs [18], sheep [25], and cattle [26]. The differences between this study and the above studies are that we selected three consecutive periods of mammary gland development.…”

“…The expression patterns of these genes found in this study were consistent with those of previous studies. [26,27], and their high expression levels may be closely related to milk synthesis during the LL and LG stages. FGF2 and FGF11, as members of the broblast growth factor family, exhibited similar expression patterns, and their expression levels were lower in the LL stage than in the DP and LG stages.…”

Genome-wide identification and expression analysis of the Collagen family during lactation in water buffalo (Bubalus Bubalis)

“…These results were also supported by the qRT-PCR. Interestingly, Dai et al [45] found that COL8A1 and COL1A2 both were upregulated in the bovine mammary gland during lactation compared to the dry period. Our findings suggested that these buffalo collagen genes displayed the specific biology function at different stages of mammary gland development.…”