title: Normal establishment of epithelial tight junctions in mice and cultured cells lacking expression of ZO-3, a tight-junction MAGUK protein.
abstract: ZO-1, ZO-2, and ZO-3 are closely related MAGUK family proteins that localize at the cytoplasmic surface of tight junctions (TJs). ZO-1 and ZO-2 are expressed in both epithelia and endothelia, whereas ZO-3 is exclusively expressed in epithelia. In spite of intensive studies of these TJ MAGUKs, our knowledge of their functions in vivo, especially those of ZO-3, is still fragmentary. Here, we have generated mice, as well as F9 teratocarcinoma cell lines, that do not express ZO-3 by homologous recombination. Unexpectedly, ZO-3(-/-) mice were viable and fertile, and rigorous phenotypic analyses identified no significant abnormalities. Moreover, ZO-3-deficient F9 teratocarcinoma cells differentiated normally into visceral endoderm epithelium-like cells in the presence of retinoic acid. These cells had a normal epithelial appearance, and the molecular architecture of their TJs did not appear to be affected, except that TJ localization of ZO-2 was upregulated. Suppression of ZO-2 expression by RNA interference in ZO-3(-/-) cells, however, did not affect the architecture of TJs. Furthermore, the speed with which TJs formed after a Ca(2+) switch was indistinguishable between wild-type and ZO-3(-/-) cells. These findings indicate that ZO-3 is dispensable in vivo in terms of individual viability, epithelial differentiation, and the establishment of TJs, at least in the laboratory environment.
authors.affiliation: Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. ada@mfour.med.kyoto-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Adachi
authors.forename: Akihito
authors.initials: A
authors.lastname: Inoko
authors.forename: Masaki
authors.initials: M
authors.lastname: Hata
authors.forename: Kyoko
authors.initials: K
authors.lastname: Furuse
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Umeda
authors.forename: Masahiko
authors.initials: M
authors.lastname: Itoh
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsukita
mesh_terms: D000483:Alleles; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D018274:Electroporation; D053595:Embryonic Stem Cells / Q000166:cytology / Q000473:pathology; D017353:Gene Deletion; D005822:Genetic Vectors; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D017434:Protein Structure, Tertiary; D018243:Teratocarcinoma / Q000235:genetics; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured; D062825:Zonula Occludens Proteins
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; C491774:Tjp3 protein, mouse; D062825:Zonula Occludens Proteins