title: Defective mammary gland morphogenesis in mice lacking the progesterone receptor B isoform.
abstract: Progesterone (P) regulates female reproduction via two nuclear receptors, PR-A and PR-B. Although both receptors display overlapping and distinct transcription regulatory properties, their individual physiological roles are unclear. To address the physiological role of PR-A, we generated a mouse model in which expression of PR-B was specifically ablated (PRBKO-/-). We show that selective activation of PR-A in PRBKO-/- mice is sufficient to elicit normal ovarian and uterine responses to P but results in reduced mammary gland morphogenesis. In the absence of PR-B, pregnancy-associated ductal sidebranching and lobuloalveolar development are markedly reduced due to decreased ductal and alveolar epithelial cell proliferation and decreased survival of alveolar epithelium. In an effort to elucidate the molecular genetic signaling pathways that are differentially regulated by PRs in the mammary gland, we have identified receptor activator of nuclear factor kappa B ligand (RANKL) as a paracrine mediator of P-dependent alveologenesis. Further, we demonstrate that the defects in PRBKO-/- mice are associated with an inability of PR-A to activate the RANKL signaling pathway in response to P. Our data indicate that functional interaction between PR-A and PR-B is not required for reproductive activity and that selective modulation of PR-A activity by progestin agonists may have a protective effect against both uterine and mammary gland hyperplasias.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Biserka
authors.initials: B
authors.lastname: Mulac-Jericevic
authors.forename: John P
authors.initials: JP
authors.lastname: Lydon
authors.forename: Francesco J
authors.initials: FJ
authors.lastname: DeMayo
authors.forename: Orla M
authors.initials: OM
authors.lastname: Conneely
mesh_terms: D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D004247:DNA / Q000235:genetics; D004848:Epithelium / Q000254:growth & development / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D008321:Mammary Glands, Animal / Q000254:growth & development* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010053:Ovary / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011980:Receptors, Progesterone / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014599:Uterus / Q000187:drug effects / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011980:Receptors, Progesterone; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; C101118:progesterone receptor A; C097314:progesterone receptor B; D011374:Progesterone; D004247:DNA