Unknown,Transcriptomics,Genomics,Proteomics

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Bovine mammary gene expression profiling during the onset of lactation

ABSTRACT: Lactogenesis includes two stages. Stage â begins a few weeks before parturition, and stage â¡ begins a few weeks before parturition. In order to better understand the molecular events driving lactogenesis in dairy cows, genome-wide gene expression profiling was conducted using digital gene expression profiling (DGE) on bovine mammary tissue at three time points (on approximately day 35 before parturition (-35d), day 7 before parturition (-7d) and day 3 after parturition (+3d)). Approximately 6.2 million, 5.8 million and 6.1 million 21-nt cDNA tags were sequenced in the three cDNA libraries (-35d, -7d and +3d), 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 â¥2 or â¤-2 and a false discovery rate (FDR) of â¤0.001, a total of 812 genes were significantly differentially expressed at -7d compared with -35d (stage â ). There were 234 genes upregulated and 578 genes downregulated, accounting for 28.8ï¼ and 71.2ï¼ of differentially expressed genes respectively. A total of 1,189 genes were significantly differentially expressed at +3d compared with -7d (stag â¡). Of these genes with significant expression changes, 274 (23.0ï¼) genes were upregulated. 915 (77.0ï¼) genes were downregulated. 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 cellï¼s resources towards lactation. Examination of genome-wide gene expression profiling using digital gene expression profiling (DGE) on bovine mammary tissue at three time points of approximately day 35 before parturition, day 7 before parturition and day 3 after parturition. There were 6 cows in each group. The mammary tissue from cows in the same group were pooled together for RNA isolation. The total RNA was used to sequence.

ORGANISM(S): Bos taurus

SUBMITTER: yuanyuan gao

PROVIDER: E-GEOD-44796 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Cows exposed to short day photoperiod (SD, 8L:16D) during the 60-day non-lactating period prior to parturition produce more milk in their subsequent lactation compared to cows exposed to long day photoperiod (LD,16L:8D). Although this response is well-established in dairy cows, the underlying mechanisms are not understood. We hypothesized that differential gene expression in cows exposed to SD or LD photoperiods during the dry period could be used to identify the functional basis for the subsequent increase in milk production during lactation. Pregnant, multiparous cows were maintained on a SD or LD photoperiod for 60-days prior to parturition. Mammary biopsies were obtained on days -24 and -9 relative to parturition and Affymetrix GeneChip® Bovine Genome Arrays were used to quantify gene expression. Sixty-four genes were differentially expressed (p ≤ 0.05 and fold-change ≥ |1.5|) between SD and LD treatments. Many of these genes were associated with cell growth and proliferation, or immune function. Ingenuity Pathway Analysis predicted upstream regulators to include TNF, TGFβ1, interferon γ and several interleukins. In addition, expression of 125 genes was significantly different between day -24 and day -9; those genes were associated with milk component metabolism and immune function. The interaction of photoperiod and time affected 32 genes associated with insulin-like growth factor (IGF-I) signaling. Genes differentially expressed in response to photoperiod were associated with mammary development and immune function consistent with the enhancement of milk yield in the ensuing lactation. Our results provide insight into the mechanisms by which photoperiod affects the mammary gland and subsequently lactation. Data were analyzed for the effect of photoperiod treatment (LD minus SD), time relative to parturition (day -24 minus day -9) and the interaction of photoperiod treatment and time ((LD minus SD day -9) minus (LD minus SD day -24))

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Bovine mammary gene expression profiling during the onset of lactation

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