title: Expression of the mammary gland-specific tammar wallaby early lactation protein gene is maintained in vitro in the absence of prolactin.
abstract: Marsupial ELP (early lactation protein) and its eutherian orthologue, CTI (colostrum trypsin inhibitor) are expressed in the mammary gland only for the first 100 days postpartum (Phase 2A) in the tammar wallaby and during the bovine and canine colostrogenesis period 24-36h postpartum respectively. The factors which regulate temporal ELP and CTI expression are unknown. A tammar mammary gland explant culture model was used to investigate ELP gene regulation during pregnancy and early- and mid-lactation (Phase 1, 2A and 2B respectively). Tammar ELP expression could only be manipulated in explants in vitro if the gene was already expressed in vivo. ELP expression was maximal in Phase 1 explants treated with lactogenic hormones (insulin, hydrocortisone and prolactin), but unlike LGB (β-lactoglobulin), ELP expression was maintained in insulin or insulin and hydrocortisone over a 12-day culture period. In contrast, ELP was down-regulated when cultured without hormones. ELP could not be induced in explants cultured from mid-lactation which suggested that transcriptional repressors may prevent ELP expression during this period.
authors.affiliation: Department of Zoology, The University of Melbourne, Melbourne, Victoria 3010, Australia; Cooperative Research Centre for Innovative Dairy Products, Australia; Victorian Institute of Animal Science, Department of Primary Industries, Attwood, Victoria 3049, Australia. Electronic address: epharo@unimelb.edu.au.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Pharo
mesh_terms: D000818:Animals; D003126:Colostrum / Q000737:chemistry*; D005260:Female; D005786:Gene Expression Regulation; D006854:Hydrocortisone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007774:Lactation / Q000235:genetics*; D007782:Lactoglobulins / Q000235:genetics / Q000378:metabolism; D007614:Macropodidae; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D008894:Milk Proteins / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology; D013997:Time Factors; D046509:Tissue Culture Techniques; D014158:Transcription, Genetic
chemical_list: D007328:Insulin; D007782:Lactoglobulins; D008894:Milk Proteins; D011388:Prolactin; D006854:Hydrocortisone
keywords: (phosphatidylinositol-3-kinase)/AKT; 17β-oestradiol; CAL; CSN1; CSN2; CTI; Culture; E(2); EGF; ELP; Explant; GR; HC; Hormone; I; IGF; INS; IR; LALBA; LGB; LLP; M199; MAPK; MEC; Marsupial; Medium 199; NS; PI3K; PRL; PRLR; Ph.; Phase; STAT; T(3); T(4); colostrum trypsin inhibitor; concurrent asynchronous lactation; early lactation protein; epidermal growth factor; glucocorticoid receptor; hydrocortisone; insulin; insulin gene; insulin receptor; insulin-like growth factor; late lactation protein; mammary epithelial cell; mitogen-activated protein kinase; not significant; postpartum; pp; preg; pregnancy; prolactin; prolactin receptor; signal transducer and activator of transcription; thyroxine, tetraiodothyronine; triiodothyronine; α-casein; α-lactabumin; β-casein; β-lactoglobulin