title: Tight junctions and compositionally related junctional structures in mammalian stratified epithelia and cell cultures derived therefrom.
abstract: The occurrence of extended tight junction (TJ) structures, including zonulae occludentes (ZO), and the spatial arrangement of TJ proteins in stratified mammalian epithelia has long been controversially discussed. Therefore, we have systematically examined the localization of TJ proteins in diverse stratified epithelial tissues (e.g., epidermis, heel pad, snout, gingiva, tongue, esophagus, exocervix, vagina, urothelium, cornea) of various species (human, bovine, rodents) as well as in human cell culture lines derived from stratified epithelia, by electron microscopy as well as by immunocytochemistry at both the light and the electron microscopic level, using antibodies to TJ proteins such as occludin, claudins 1 and 4, protein ZO-1, cingulin and symplekin. We have found an unexpected diversity of TJ-related structures of which only those showing colocalization with the most restricted transmembrane TJ marker protein, occludin, are presented here. While in epidermis and urothelium occludin is restricted to the uppermost living cell layer, TJ-related junctions are abundant in the upper third or even in the majority of the suprabasal cell layers in other stratified epithelia. Interfollicular epidermis contains, in the stratum granulosum, extended, probably continuous ZO-like structures which can also be traced at least through the Henle cell layer of hair follicles. Similar apical ZO-like structures have been seen in the upper living cell layers of all other stratified epithelia and cell cultures examined, but in most of them we have noticed, in addition, junctional regions showing relatively broad, ribbon-like membrane contacts which in cross-section often appear pentalaminar, with an electron-dense middle lamella ("lamellated TJs", coniunctiones laminosae). In suprabasal layers of several stratified epithelia we have further observed TJ protein-containing junctions of variable sizes which are characterized by a 10-30-nm dense lamina interposed between the two membranes ("sandwich junctions"; iuncturae structae). Moreover, we have often observed variously sized regions in which the intermembrane distance is rather regularly bridged by short rod-like elements ("cross-bridged cell walls"; parietes transtillati), often in close vicinity of TJ-related structures or desmosomes. The significance of these structures and their possible biological importance are discussed.
authors.affiliation: Division of Cell Biology, German Cancer Research Center, Heidelberg.
authors.forename: Lutz
authors.initials: L
authors.lastname: Langbein
authors.forename: Christine
authors.initials: C
authors.lastname: Grund
authors.forename: Caecilia
authors.initials: C
authors.lastname: Kuhn
authors.forename: Silke
authors.initials: S
authors.lastname: Praetzel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kartenbeck
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Brandner
authors.forename: Ingrid
authors.initials: I
authors.lastname: Moll
authors.forename: Werner W
authors.initials: WW
authors.lastname: Franke
mesh_terms: D000328:Adult; D000818:Animals; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D062445:Claudin-1; D062506:Claudin-4; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure*; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure*; D005260:Female; D005333:Fetus; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D009687:Nuclear Proteins; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D011247:Pregnancy; D011506:Proteins / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism / Q000648:ultrastructure*; D014407:Tumor Cells, Cultured; D062826:Zonula Occludens-1 Protein
chemical_list: C061407:CGN protein, human; C568108:CLDN1 protein, human; C568157:CLDN4 protein, human; D062445:Claudin-1; D062506:Claudin-4; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; D011506:Proteins; C101043:SYMPK protein, human; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein