title: Cell-matrix interactions during development and apoptosis of the mouse mammary gland in vivo.
abstract: Epithelial cell survival is dependent on extracellular signals provided by both soluble factors and by adhesion. In the mammary gland, extensive apoptosis of epithelial cells occurs rapidly when lactation ceases, but the mechanism of apoptosis induction is not known. In tissue culture, mammary epithelial cells require laminin as a survival ligand and specific beta1 integrins are necessary to suppress apoptosis. To explore the possibility that dynamic changes in cell-matrix interactions contribute to the onset of apoptosis during mammary involution in vivo, a detailed immunohistochemical analysis of the expression of integrin subunits and their extracellular matrix ligands during mouse mammary gland development has been performed. The kinetics of apoptosis were determined by using tissue samples obtained from virgin, pregnant, lactating, and involuting gland. The maximal elevation of apoptosis occurred within 24 hr of weaning as determined by histologic analysis and caspase-3 staining. A wide variety of laminin subunits, together with nidogen-1 and -2, and perlecan were identified within the basement membrane region of epithelial ducts, lobules, and alveoli in both human and mouse mammary gland. However, no change in the distribution of any of the basement membrane proteins or their cognate integrin receptors was observed during the transition from lactation to apoptosis. Instead, we discovered that altered ligand-binding conformation of the beta1 integrin to a nonbinding state coincided with the immediate onset of mammary apoptosis. This finding may provide a novel dynamic mechanism for inhibiting the transduction of extracellular matrix survival signals, thereby contributing to the onset of apoptosis in a developmental context in vivo.
authors.affiliation: School of Biological Sciences, University of Manchester, Oxford Road, Manchester, United Kingdom.
authors.forename: Janine M
authors.initials: JM
authors.lastname: Prince
authors.forename: Teresa C M
authors.initials: TC
authors.lastname: Klinowska
authors.forename: Emma
authors.initials: E
authors.lastname: Marshman
authors.forename: Emma T
authors.initials: ET
authors.lastname: Lowe
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mayer
authors.forename: Jeff
authors.initials: J
authors.lastname: Miner
authors.forename: Daniel
authors.initials: D
authors.lastname: Aberdam
authors.forename: Dietmar
authors.initials: D
authors.lastname: Vestweber
authors.forename: Barry
authors.initials: B
authors.lastname: Gusterson
authors.forename: Charles H
authors.initials: CH
authors.lastname: Streuli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D017209:Apoptosis; D001940:Breast / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000096:biosynthesis; D015815:Cell Adhesion Molecules; D005260:Female; D019812:Heparan Sulfate Proteoglycans / Q000096:biosynthesis; D006801:Humans; D039421:Integrin alpha2; D039422:Integrin alpha3; D039503:Integrin alpha6; D019012:Integrin beta1 / Q000096:biosynthesis; D016023:Integrins / Q000096:biosynthesis; D007774:Lactation; D007797:Laminin / Q000096:biosynthesis; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D008813:Mice, Inbred ICR; D008969:Molecular Sequence Data; D011247:Pregnancy
chemical_list: D015703:Antigens, CD; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D019812:Heparan Sulfate Proteoglycans; D039421:Integrin alpha2; D039422:Integrin alpha3; D039503:Integrin alpha6; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D008562:Membrane Glycoproteins; C114729:NID2 protein, human; C029967:nidogen; C071927:perlecan