Bovine Mammary Gene Expression Profiling during the Onset of Lactation

Yuanyuan Gao,Kerong Shi,Zhonghua Wang,Xueyan Lin,Zhengui Yan,Marinus F W Te Pas

doi:10.1371/journal.pone.0070393

Yuanyuan Gao, Kerong Shi + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0070393

Copy DOI

Journal: PloS one	Publication Date: Aug 21, 2013
Citations: 39	License type: CC BY 4.0

Affiliation: Shandong Agricultural University

Abstract

BackgroundLactogenesis includes two stages. Stage I begins a few weeks before parturition. Stage II is initiated around the time of parturition and extends for several days afterwards.Methodology/Principal FindingsTo better understand the molecular events underlying these changes, genome-wide gene expression profiling was conducted using digital gene expression (DGE) on bovine mammary tissue at three time points (on approximately day 35 before parturition (−35 d), day 7 before parturition (−7 d) and day 3 after parturition (+3 d)). Approximately 6.2 million (M), 5.8 million (M) and 6.1 million (M) 21-nt cDNA tags were sequenced in the three cDNA libraries (−35 d, −7 d and +3 d), respectively. After aligning to the reference sequences, the three cDNA libraries included 8,662, 8,363 and 8,359 genes, respectively. With a fold change cutoff criteria of ≥2 or ≤−2 and a false discovery rate (FDR) of ≤0.001, a total of 812 genes were significantly differentially expressed at −7 d compared with −35 d (stage I). Gene ontology analysis showed that those significantly differentially expressed genes were mainly associated with cell cycle, lipid metabolism, immune response and biological adhesion. A total of 1,189 genes were significantly differentially expressed at +3 d compared with −7 d (stage II), and these genes were mainly associated with the immune response and cell cycle. Moreover, there were 1,672 genes significantly differentially expressed at +3 d compared with −35 d. Gene ontology analysis showed that the main differentially expressed genes were those associated with metabolic processes.ConclusionsThe results suggest that the mammary gland begins to lactate not only by a gain of function but also by a broad suppression of function to effectively push most of the cell's resources towards lactation.

Highlights

Lactating cows are generally dried off by stopping the milking process approximately two months before the parturition
The results suggest that the mammary gland begins to lactate by a gain of function and by a broad suppression of function to effectively push most of the cell’s resources towards lactation
The mammary gland undergoes an involution process, which is marked by the cessation of secretory activity and the reabsorption of milk residue, followed by a relatively static period

Summary

Introduction

Lactating cows are generally dried off by stopping the milking process approximately two months before the parturition. The mammary gland does not resume its activity until approximately 2 to 3 weeks before the parturition, when dramatic changes occur to prepare for profuse milk secretion after parturition. Lactogenesis is defined as the process from the resumption of mammary activity until profuse milk secretion and is divided into two stages [4]. Stage I is the period from the resumption of mammary activity to the time of parturition and is characterized by mammary differentiation, proliferation, and progressive expression of milk protein, as well as the secretion of precolostrum. Stage II is initiated around the time of parturition and extends for several days afterwards This stage is characterized by the closure of the tight junctions between alveolar cells and the formation and secretion of colostrum and milk.

Objectives

Methods

Results

Conclusion