title: Short communication: A milk trait-associated polymorphism in the bovine growth hormone receptor gene does not affect receptor signaling.
abstract: Growth hormone (GH), also known as somatotropin, stimulates milk production in cows. At the tissue level, the action of GH is mediated by the GH receptor (GHR) and the receptor-activated intracellular signaling pathway involving Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5). A T/A nucleotide variation in exon 8 of the bovine GHR gene, resulting in a phenylalanine to tyrosine change in the transmembrane domain of the GHR protein, has been reported to be associated with a major effect on milk yield in cows. The objective of this study was to determine whether the 2 versions of GHR differ in mediating GH-induced STAT5 activation of gene expression. We created cDNA expression plasmids for the 2 versions of GHR and cotransfected each of them with a STAT5 expression plasmid and a luciferase reporter gene construct containing STAT5 binding sites into 2 different cell lines. Treatment of the transfected cells with various concentrations of GH triggered a dose-dependent increase in luciferase activity. However, the GH-induced luciferase activity was not different between the 2 GHR expression plasmids, indicating that the 2 GHR forms did not differ in mediating GH-induced STAT5 activation of gene expression. Thus, if the T/A polymorphism in exon 8 of the GHR gene has a causative effect on milk production, this effect is unlikely to be mediated by the JAK2-STAT5 pathway, the currently known major signaling pathway from the growth hormone receptor.
authors.affiliation: Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhou
authors.forename: H
authors.initials: H
authors.lastname: Jiang
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015870:Gene Expression; D013006:Growth Hormone / Q000494:pharmacology; D053614:Janus Kinase 2; D007774:Lactation / Q000235:genetics*; D011110:Polymorphism, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D040641:Quantitative Trait Loci; D011986:Receptors, Somatotropin / Q000235:genetics* / Q000502:physiology; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
chemical_list: D018076:DNA, Complementary; D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin; D050799:STAT5 Transcription Factor; D013006:Growth Hormone; D011505:Protein-Tyrosine Kinases; D053614:Janus Kinase 2