title: Hormonal regulation of platypus Beta-lactoglobulin and monotreme lactation protein genes.
abstract: Endocrine regulation of milk protein gene expression in marsupials and eutherians is well studied. However, the evolution of this complex regulation that began with monotremes is unknown. Monotremes represent the oldest lineage of extant mammals and the endocrine regulation of lactation in these mammals has not been investigated. Here we characterised the proximal promoter and hormonal regulation of two platypus milk protein genes, Beta-lactoglobulin (BLG), a whey protein and monotreme lactation protein (MLP), a monotreme specific milk protein, using in vitro reporter assays and a bovine mammary epithelial cell line (BME-UV1). Insulin and dexamethasone alone provided partial induction of MLP, while the combination of insulin, dexamethasone and prolactin was required for maximal induction. Partial induction of BLG was achieved by insulin, dexamethasone and prolactin alone, with maximal induction using all three hormones. Platypus MLP and BLG core promoter regions comprised transcription factor binding sites (e.g. STAT5, NF-1 and C/EBPα) that were conserved in marsupial and eutherian lineages that regulate caseins and whey protein gene expression. Our analysis suggests that insulin, dexamethasone and/or prolactin alone can regulate the platypus MLP and BLG gene expression, unlike those of therian lineage. The induction of platypus milk protein genes by lactogenic hormones suggests they originated before the divergence of marsupial and eutherians.
authors.affiliation: School of Medicine, Deakin University, 75 Pigdons Road, Waurn Ponds, Geelong, Victoria 3216, Australia. Electronic address: ashwantha.enjapoori@deakin.edu.au.
authors.forename: Ashwantha Kumar
authors.initials: AK
authors.lastname: Enjapoori
authors.affiliation: School of Medicine, Deakin University, 75 Pigdons Road, Waurn Ponds, Geelong, Victoria 3216, Australia. Electronic address: christophe.lefevre@deakin.edu.au.
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Lefèvre
authors.affiliation: School of Medicine, Deakin University, 75 Pigdons Road, Waurn Ponds, Geelong, Victoria 3216, Australia; Department of Anatomy and Cell Biology, Monash University, Clayton, Victoria 3800, Australia. Electronic address: kevin.nicholas@deakin.edu.au.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Nicholas
authors.affiliation: School of Medicine, Deakin University, 75 Pigdons Road, Waurn Ponds, Geelong, Victoria 3216, Australia; Department of Anatomy and Cell Biology, Monash University, Clayton, Victoria 3800, Australia; Institute for Frontier Materials, Deakin University, 75 Pigdons Road, Waurn Ponds, Geelong, Victoria 3216, Australia. Electronic address: julie.sharp@deakin.edu.au.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Sharp
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002364:Caseins / Q000235:genetics; D003907:Dexamethasone / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D007328:Insulin / Q000378:metabolism; D007774:Lactation / Q000502:physiology*; D007782:Lactoglobulins / Q000235:genetics / Q000378:metabolism*; D010987:Platypus / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D002364:Caseins; D007328:Insulin; D007782:Lactoglobulins; D014157:Transcription Factors; D003907:Dexamethasone; D011388:Prolactin
keywords: Echidna; Hormonal regulation; Milk protein gene expression; Monotreme lactation protein; Platypus; Platypus Beta-lactoglobulin gene