title: Bovine mammary gene expression profiling during the onset of lactation.
abstract: BACKGROUND
  Lactogenesis 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.
  
  
  RESULTS
  To 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Shandong Provincial Key Laboratory of Ruminant Nutritional Physiology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Taian, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Xueyan
authors.initials: X
authors.lastname: Lin
authors.forename: Kerong
authors.initials: K
authors.lastname: Shi
authors.forename: Zhengui
authors.initials: Z
authors.lastname: Yan
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000465:Algorithms; D000818:Animals; D002417:Cattle; D016000:Cluster Analysis; D003612:Dairying; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D015723:Gene Library; D007774:Lactation / Q000235:genetics* / Q000502:physiology*; D050356:Lipid Metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D036801:Parturition; D012313:RNA / Q000032:analysis; D017422:Sequence Analysis, DNA; D013997:Time Factors
chemical_list: D012313:RNA