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Gene expression of the teat canal epithelium in dry and lactating cows
Notcovich, S.; Williamson, N...
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Objectives: A keratin plug is formed in the teat canal during the dry period and protects the mammary gland against infections. However, mastitis incidence during the early dry period is high. Information about the variation of gene expression in the teat canal epithelium could provide insights into the physiology of the keratin plug formation during the early dry period.
The objective of this study was to identify differences in gene expression in teat canal biopsy samples obtained at different time points during the early dry period and early lactation.
Materials and methods: In a first study (Experiment 1), the gene expression of teat canal samples from five cows in late lactation to early dry period were analysed. Samples from Day 0 (dry off day) and Day 11 of the dry period were compared using RNA-Seq. Genes differentially expressed between Day 0 and Day 11 samples were selected for further analysis. The RNA-Seq results were used to select 42 relevant genes including nine keratin genes of interest that were analysed for variation of gene expression in Experiment 2 by Nanostring nCounter. Repeated teat canal biopsy samples obtained from eight cows on days 0, 7, and 21 of the dry period, and on approximately days 10 and 25 after calving (Day 70 and 90) were also analysed. Oral mucosa samples were taken at the same time-points to serve as controls.
Results: Experiment 1 identified 36 differentially expressed genes of the teat canal epithelium at dry off (Day 0) and Day 11. Twenty-two of the genes were downregulated. Gene ontology enrichment analyses revealed that these genes were mainly related to binding, adherence, and RNA transcription factors. Analysis of individual gene functions showed that they were genes involved in mitosis and immune response pathways. Results from Experiment 2 showed dif- ferent patterns of expression of the genes between the teat canal and the oral tissue (control) over time. Genes NR4R, KRT17, CSRP2, KIF23, TRPS1, LOC107131159, and TFPI2 were downregulated 7 days after drying off whereas RBB- P8NL, PKIB, MARKS, TLR5, BAZ1A, IRX3, KRT4, PADI1, PENK, RND3, SERPINA1, SYT17 only presented differences after calving (p<0.05) in the teat tissue. The expression levels of the genes in a comparison of the results of both methods (Illumina and Nanostring) coincided, suggesting a decrease in gene expression after drying off in the teat canal related to cellular functions such as binding, adhesion, mitosis and immune response.
Conclusion: Modern gene expression analysis of the experiments reported in this study suggests that cell proliferation and immune response of epithelial tissue in the teat canal decrease during the early dry period and there is a major reactivation of gene expression after calving. The pathways affected might contribute to the higher incidence of mastitis during the early dry period. To our knowledge, this is the first study to investigate changes in gene expression of the teat canal epithelium during the early dry and lactating period. Further detailed studies on the physiology of the teat canal and keratin plug formation would be required for developing strategies to improve the immune response of cows against mastitis in the early dry period with the aim of decreasing the incidence of mammary infections.
Keywords: Keratin plug, dry off period, gene expression, teat canal.
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Affiliation of the authors at the time of publication
Massey University, School of Veterinary Sciences, New Zealand;
Department of Primary Industries, NSW, Australia;
AgResearch, Palmerston North, New Zealand;
Wageningen University, GD Animal Health, Netherlands;
Massey University, Epi Centre, New Zealand.
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