title: Functional development of the adult ovine mammary gland--insights from gene expression profiling.
abstract: BACKGROUND
  The mammary gland is a dynamic organ that undergoes dramatic physiological adaptations during the transition from late pregnancy to lactation. Investigation of the molecular basis of mammary development and function will provide fundamental insights into tissue remodelling as well as a better understanding of milk production and mammary disease. This is important to livestock production systems and human health. Here we use RNA-seq to identify differences in gene expression in the ovine mammary gland between late pregnancy and lactation.
  
  
  RESULTS
  Between late pregnancy (135 days of gestation ± 2.4 SD) and lactation (15 days post partum ± 1.27 SD) 13 % of genes in the sheep genome were differentially expressed in the ovine mammary gland. In late pregnancy, cell proliferation, beta-oxidation of fatty acids and translation were identified as key biological processes. During lactation, high levels of milk fat synthesis were mirrored by enrichment of genes associated with fatty acid biosynthesis, transport and lipogenesis. Protein processing in the endoplasmic reticulum was enriched during lactation, likely in support of active milk protein synthesis. Hormone and growth factor signalling and activation of signal transduction pathways, including the JAK-STAT and PPAR pathways, were also differently regulated, indicating key roles for these pathways in functional development of the ovine mammary gland. Changes in the expression of epigenetic regulators, particularly chromatin remodellers, indicate a possible role in coordinating the large-scale transcriptional changes that appear to be required to switch mammary processes from growth and development during late pregnancy to synthesis and secretion of milk during lactation.
  
  
  CONCLUSIONS
  Coordinated transcriptional regulation of large numbers of genes is required to switch between mammary tissue establishment during late pregnancy, and activation and maintenance of milk production during lactation. Our findings indicate the remarkable plasticity of the mammary gland, and the coordinated regulation of multiple genes and pathways to begin milk production. Genes and pathways identified by the present study may be important for managing milk production and mammary development, and may inform studies of diseases affecting the mammary gland.
authors.affiliation: Laboratory for Evolution and Development, Genetics Otago, Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, Aotearoa, New Zealand. A.M.Paten@massey.ac.nz.|International Sheep Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Aotearoa, New Zealand. A.M.Paten@massey.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. A.M.Paten@massey.ac.nz.
authors.forename: Amy M
authors.initials: AM
authors.lastname: Paten
authors.affiliation: Laboratory for Evolution and Development, Genetics Otago, Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, Aotearoa, New Zealand. elizabeth.duncan@otago.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. elizabeth.duncan@otago.ac.nz.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Duncan
authors.affiliation: International Sheep Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Aotearoa, New Zealand. S.J.Pain@massey.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. S.J.Pain@massey.ac.nz.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Pain
authors.affiliation: International Sheep Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Aotearoa, New Zealand. S.Peterson@massey.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. S.Peterson@massey.ac.nz.
authors.forename: Sam W
authors.initials: SW
authors.lastname: Peterson
authors.affiliation: International Sheep Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Aotearoa, New Zealand. P.R.Kenyon@massey.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. P.R.Kenyon@massey.ac.nz.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Kenyon
authors.affiliation: International Sheep Research Centre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Aotearoa, New Zealand. H.Blair@massey.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. H.Blair@massey.ac.nz.
authors.forename: Hugh T
authors.initials: HT
authors.lastname: Blair
authors.affiliation: Laboratory for Evolution and Development, Genetics Otago, Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, Aotearoa, New Zealand. peter.dearden@otago.ac.nz.|Gravida; National Centre for Growth and Development, Auckland, New Zealand. peter.dearden@otago.ac.nz.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Dearden
mesh_terms: D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002470:Cell Survival; D019295:Computational Biology / Q000379:methods; D004734:Energy Metabolism / Q000235:genetics; D044127:Epigenesis, Genetic; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007774:Lactation / Q000235:genetics; D008321:Mammary Glands, Animal / Q000254:growth & development / Q000378:metabolism*; D008954:Models, Biological; D011247:Pregnancy; D014176:Protein Biosynthesis; D012756:Sheep; D059467:Transcriptome