The extracellular matrix (ECM) plays an important role in mammary gland development and function. Osteopontin (OPN), a secreted glycophosphoprotein, with several functional and structural properties of ECM proteins, is expressed at elevated levels during normal and pathologic development of the mammary gland and is present in milk. However, whether it plays any developmental role in the mammary gland is unknown. To investigate this possibility, transgenic AS-OPN mice were generated using a transgene expressing OPN antisense RNA under the control of the MMTV-LTR promoter/enhancer. The mammary glands of AS-OPN mice express low levels of OPN, compared to control littermates, show excessive branching of the ductal epithelium at the virgin stage, impaired proliferation of the mammary epithelium, and abnormal alveolar structure formation during pregnancy, and mild to severe lactation deficiency. To further examine the role of OPN at the cellular level, an established murine mammary epithelial cell line (NMuMG), which is capable of differentiation in culture, was transfected with the same DNA construct used to generate AS-OPN mice. Several antisense OPN cDNA transfected clones, which secrete decreased amounts of OPN compared to mock-transfected cells were obtained. These cells were found to have lost their ability to form branched duct-like structures, as judged by branching morphogenesis assays, by growth in collagen gels and stimulation with hepatocyte growth factor. They also failed to spread on type I collagen, although their binding to type IV collagen was unaffected. The antisense transfectants also assumed a mesenchymal phenotype, characterized by fibroblast-like morphology, an apparent loss of cell-cell contacts and spontaneous cell scattering. Transmigration assays and wounding experiments indicated that these cells also have a higher migratory activity than control cells. Northern blot and immunofluorescence analyses showed that migrating cells downregulate OP
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35026 |
| Date | January 1998 |
| Creators | Nemir, Mohamed. |
| Contributors | Mukherjee, B. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001643047, proquestno: NQ44529, Theses scanned by UMI/ProQuest. |
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