title: Mechanisms of modulation of the Egr gene family in mammary epithelial cells of different species.
abstract: In the adult female, within the estrous cycle, the mammary gland undergoes multiple rounds of growth, with increased cellular proliferation, and involution, with increased apoptosis. The increase in proliferation is elicited by endocrine (Estrogen, Progesterone), as well as locally produced (epidermal growth factor, insulin-like growth factor, etc) growth factors. Among the genes that are modulated during cellular proliferation, immediate early genes play a fundamental role, being rapidly upregulated and then downregulated within the G0/G1 phase of the cell cycle, allowing the progression to the subsequent phases. Egrs (1-4) are immediate early genes that encode for transcription factors that promote, within different cell types and depending on the strength and duration of the stimuli, several different responses like mitogenesis, differentiation, apoptosis or even anti-apoptosis. In this work we have studied the mechanisms of modulation of the Egr family, in mammary epithelial cells of different origin (bovine, canine, feline, murine). Following stimulation with growth medium, Egr mRNA expression showed a strong upregulation reaching a peak at 45-60min, that rapidly declined. Among several cytokines, particularly important for mammary morphogenesis, that we have tested (EGF, IGF-I, insulin, estrogen, progesterone), only EGF upregulated Egrs to levels close to those elicited by growth medium. In order to understand how the Egr transcription factors were regulated, we have inhibited Erk 1/2 and PI3K, molecules that drive two major intracellular signaling pathways. Inhibition of the Erk 1/2 pathway totally abolished Egr upregulation mediated by growth medium or EGF. On the other hand, the PI3K-Akt pathway played a minor role on Egr levels, with a strong inhibitory effect on cat GH2 cells only, that could be ascribed to reduced Erk phosphorylation following PI3K inhibition. Finally we showed that addition of growth medium also upregulated that the mammary luminal marker cytokeratin 18, but only in the murine NMuMG cell line. This is the first manuscript describing how the Egr transcription factors are expressed in mammary epithelial cells of domestic animals and which growth factors and signaling pathways modulate their expression.
authors.affiliation: Dipartimento di Scienze Veterinarie, Largo Braccini 2, 10095 Grugliasco (TO), Italy. Electronic address: paolo.santino@unito.it.
authors.forename: P
authors.initials: P
authors.lastname: Santino
authors.affiliation: Dipartimento di Scienze Veterinarie, Largo Braccini 2, 10095 Grugliasco (TO), Italy. Electronic address: eugenio.martignani@unito.it.
authors.forename: E
authors.initials: E
authors.lastname: Martignani
authors.affiliation: Dipartimento di Scienze Veterinarie, Largo Braccini 2, 10095 Grugliasco (TO), Italy. Electronic address: silvia.miretti@unito.it.
authors.forename: S
authors.initials: S
authors.lastname: Miretti
authors.affiliation: Dipartimento di Scienze Veterinarie, Largo Braccini 2, 10095 Grugliasco (TO), Italy. Electronic address: mario.baratta@unito.it.
authors.forename: M
authors.initials: M
authors.lastname: Baratta
authors.affiliation: Dipartimento di Scienze Veterinarie, Largo Braccini 2, 10095 Grugliasco (TO), Italy. Electronic address: paolo.accornero@unito.it.
authors.forename: P
authors.initials: P
authors.lastname: Accornero
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D051765:Early Growth Response Transcription Factors / Q000235:genetics* / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D053538:Keratin-18 / Q000235:genetics / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology*; D005810:Multigene Family; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D051765:Early Growth Response Transcription Factors; D036341:Intercellular Signaling Peptides and Proteins; D053538:Keratin-18; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: Egr; Epidermal growth factor; Immediate early gene; Mammary gland; Proliferation