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      Tight junctions in Schwann cells of peripheral myelinated axons : a lesson from claudin-19–deficient mice

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          Abstract

          Tight junction (TJ)–like structures have been reported in Schwann cells, but their molecular composition and physiological function remain elusive. We found that claudin-19, a novel member of the claudin family (TJ adhesion molecules in epithelia), constituted these structures. Claudin-19–deficient mice were generated, and they exhibited behavioral abnormalities that could be attributed to peripheral nervous system deficits. Electrophysiological analyses showed that the claudin-19 deficiency affected the nerve conduction of peripheral myelinated fibers. Interestingly, the overall morphology of Schwann cells lacking claudin-19 expression appeared to be normal not only in the internodal region but also at the node of Ranvier, except that TJs completely disappeared, at least from the outer/inner mesaxons. These findings have indicated that, similar to epithelial cells, Schwann cells also bear claudin-based TJs, and they have also suggested that these TJs are not involved in the polarized morphogenesis but are involved in the electrophysiological “sealing” function of Schwann cells.

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          Most cited references55

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          Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction.

          A new method of total RNA isolation by a single extraction with an acid guanidinium thiocyanate-phenol-chloroform mixture is described. The method provides a pure preparation of undegraded RNA in high yield and can be completed within 4 h. It is particularly useful for processing large numbers of samples and for isolation of RNA from minute quantities of cells or tissue samples.
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            Claudin-1 and -2: Novel Integral Membrane Proteins Localizing at Tight Junctions with No Sequence Similarity to Occludin

            Occludin is the only known integral membrane protein localizing at tight junctions (TJ), but recent targeted disruption analysis of the occludin gene indicated the existence of as yet unidentified integral membrane proteins in TJ. We therefore re-examined the isolated junction fraction from chicken liver, from which occludin was first identified. Among numerous components of this fraction, only a broad silver-stained band ∼22 kD was detected with the occludin band through 4 M guanidine-HCl extraction as well as sonication followed by stepwise sucrose density gradient centrifugation. Two distinct peptide sequences were obtained from the lower and upper halves of the broad band, and similarity searches of databases allowed us to isolate two full-length cDNAs encoding related mouse 22-kD proteins consisting of 211 and 230 amino acids, respectively. Hydrophilicity analysis suggested that both bore four transmembrane domains, although they did not show any sequence similarity to occludin. Immunofluorescence and immunoelectron microscopy revealed that both proteins tagged with FLAG or GFP were targeted to and incorporated into the TJ strand itself. We designated them as “claudin-1” and “claudin-2”, respectively. Although the precise structure/function relationship of the claudins to TJ still remains elusive, these findings indicated that multiple integral membrane proteins with four putative transmembrane domains, occludin and claudins, constitute TJ strands.
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              The tight junction: a multifunctional complex.

              Multicellular organisms are separated from the external environment by a layer of epithelial cells whose integrity is maintained by intercellular junctional complexes composed of tight junctions, adherens junctions, and desmosomes, whereas gap junctions provide for intercellular communication. The aim of this review is to present an updated overview of recent developments in the area of tight junction biology. In a relatively short time, our knowledge of the tight junction has evolved from a relatively simple view of it being a permeability barrier in the paracellular space and a fence in the plane of the plasma membrane to one of it acting as a multicomponent, multifunctional complex that is involved in regulating numerous and diverse cell functions. A group of integral membrane proteins-occludin, claudins, and junction adhesion molecules-interact with an increasingly complex array of tight junction plaque proteins not only to regulate paracellular solute and water flux but also to integrate such diverse processes as gene transcription, tumor suppression, cell proliferation, and cell polarity.
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                Author and article information

                Journal
                J Cell Biol
                The Journal of Cell Biology
                The Rockefeller University Press
                0021-9525
                1540-8140
                9 May 2005
                : 169
                : 3
                : 527-538
                Affiliations
                [1 ]Department of Cell Biology, Horizontal Medical Research Organization
                [2 ]Genetic Engineering and Functional Genomics Group, Horizontal Medical Research Organization
                [3 ]Department of Dermatology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
                [4 ]Department of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
                [5 ]KAN Research Institute Inc., Kyoto Research Park, Chudoji, Shimogyo-ku, Kyoto 600-8317, Japan
                [6 ]Section of Developmental Neurophysiology, Ozaki Institute for Integrative Bioscience, National Institute of Natural Sciences, Okazaki 444-8787, Japan
                [7 ]Department of Molecular Cell Biology, Institute of DNA Medicine, The Jikei University School of Medicine, Nishi-Shinbashi, Minato-ku, Tokyo 105, Japan
                Author notes

                Correspondence to Shoichiro Tsukita: htsukita@ 123456mfour.med.kyoto-u.ac.jp

                Article
                200501154
                10.1083/jcb.200501154
                2171943
                15883201
                12ee0af4-b2b3-4b8a-a828-d5969db78ec1
                Copyright © 2005, The Rockefeller University Press
                History
                : 31 January 2005
                : 18 March 2005
                Categories
                Research Articles
                Article

                Cell biology
                Cell biology

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