title: Mammary collective cell migration involves transient loss of epithelial features and individual cell migration within the epithelium.
abstract: Normal mammary morphogenesis involves transitions between simple and multilayered epithelial organizations. We used electron microscopy and molecular markers to determine whether intercellular junctions and apico-basal polarity were maintained in the multilayered epithelium. We found that multilayered elongating ducts had polarized apical and basal tissue surfaces both in three-dimensional culture and in vivo. However, individual cells were only polarized on surfaces in contact with the lumen or extracellular matrix. The basolateral marker scribble and the apical marker atypical protein kinase C zeta localized to all interior cell membranes, whereas PAR3 displayed a cytoplasmic localization, suggesting that the apico-basal polarity was incomplete. Despite membrane localization of E-cadherin and β-catenin, we did not observe a defined zonula adherens connecting interior cells. Instead, interior cells were connected through desmosomes and exhibited complex interdigitating membrane protrusions. Single-cell labeling revealed that individual cells were both protrusive and migratory within the epithelial multilayer. Inhibition of Rho kinase (ROCK) further reduced intercellular adhesion on apical and lateral surfaces but did not disrupt basal tissue organization. Following morphogenesis, segregated membrane domains were re-established and junctional complexes re-formed. We observed similar epithelial organization during mammary morphogenesis in organotypic culture and in vivo. We conclude that mammary epithelial morphogenesis involves a reversible, spatially limited, reduction in polarity and intercellular junctions and active individualistic cell migration. Our data suggest that reductions in polarity and adhesion during breast cancer progression might reflect partial recapitulation of a normal developmental program.
authors.affiliation: Department of Anatomy, University of California-San Francisco, San Francisco, CA 94143, USA. andrew.ewald@jhmi.edu
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ewald
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Huebner
authors.forename: Hildur
authors.initials: H
authors.lastname: Palsdottir
authors.forename: Jessie K
authors.initials: JK
authors.lastname: Lee
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Perez
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Jorgens
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Tauscher
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Cheung
authors.forename: Zena
authors.initials: Z
authors.lastname: Werb
authors.forename: Manfred
authors.initials: M
authors.lastname: Auer
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002450:Cell Communication / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002465:Cell Movement / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D022081:Cell Surface Extensions / Q000378:metabolism / Q000648:ultrastructure; D003094:Collagen; D003896:Desmosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004338:Drug Combinations; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D005260:Female; D007797:Laminin; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000254:growth & development / Q000648:ultrastructure; D051379:Mice; D008954:Models, Biological; D009024:Morphogenesis / Q000187:drug effects; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009940:Organoids / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D011509:Proteoglycans; D011725:Pyridines / Q000494:pharmacology; D019108:Tight Junctions / Q000378:metabolism / Q000648:ultrastructure; D046509:Tissue Culture Techniques; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000577:Amides; D004338:Drug Combinations; D007797:Laminin; D011509:Proteoglycans; D011725:Pyridines; C059485:matrigel; C108830:Y 27632; D003094:Collagen; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase; D020744:rac GTP-Binding Proteins