title: Integrin and dystroglycan compensate each other to mediate laminin-dependent basement membrane assembly and epiblast polarization.
abstract: During early embryogenesis, endodermal γ1-laminin expression is required for basement membrane (BM) assembly, promoting conversion of non-polar pluripotent cells into polarized epiblast. The influence of laminin-111 (Lm111) and its integrin and dystroglycan (DG) receptors on epiblast in embryoid bodies (EBs), a model for differentiation of the embryonic plate, was further investigated. Lm111 added to the medium of EBs initiated conversion of inner nonpolar cell to the polarized epiblast epithelium with an exterior-to-central basal-to-apical orientation. Microinjection of Lm111 into EB interiors resulted in an interior BM with complete inversion of cell polarity. Lm111 assembled a BM on integrin-β1 null EBs with induction of polarization at reduced efficiency. β-Integrin compensation was not detected in these nulls with integrin adaptor proteins failing to assemble. A dimer of laminin LG domains 4-5 (LZE3) engineered to strongly bind to α-dystroglycan almost completely inhibited laminin accumulation on integrin β1-null EBs, reducing BM and ablating cell polarization. When Lm111 was incubated with integrin-β1/dystroglycan double-knockout EBs, laminin failed to accumulate on the EBs, the EBs did not differentiate, and the EBs underwent apoptosis. Collectively the findings support the hypotheses that the locus of laminin cell surface assembly can determine the axis of epithelial polarity. This requires integrin- and/or dystroglycan-dependent binding to laminin LG domains with the highest efficiency achieved when both receptors are present. Finally, EBs that cannot assemble a matrix undergo apoptosis.
authors.affiliation: Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA; Department of Pathology & Laboratory Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA. Electronic address: shaohua.li@rutgers.edu.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Qi
authors.affiliation: Department of Pathology & Laboratory Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: McKee
authors.affiliation: Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.
authors.forename: June
authors.initials: J
authors.lastname: Hsu
authors.affiliation: Department of Pathology & Laboratory Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA. Electronic address: yurchenc@rwjms.rutgers.edu.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Yurchenco
mesh_terms: D000818:Animals; D017209:Apoptosis; D001485:Basement Membrane / Q000378:metabolism*; D002454:Cell Differentiation; D016764:Cell Polarity; D049030:Dystroglycans / Q000172:deficiency / Q000235:genetics*; D004622:Embryo, Mammalian; D058732:Embryoid Bodies / Q000378:metabolism* / Q000473:pathology; D047108:Embryonic Development / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D017353:Gene Deletion; D005786:Gene Expression Regulation; D005855:Germ Layers / Q000166:cytology / Q000378:metabolism*; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism; D007797:Laminin / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D019012:Integrin beta1; D007797:Laminin; D020033:Protein Isoforms; C089141:laminin gamma 1; D049030:Dystroglycans
keywords: cell polarity; embryonic stem cell; endoderm; epiblast