Differential Expression of the Tight Junction Proteins, Claudin-1, Claudin-4, Occludin, ZO-1, and PAR3, in the Ameloblasts of Rat Upper Incisors

Authors

  • Tetsuichiro Inai,

    Corresponding author
    1. Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
    • Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, 812-8582 Fukuoka, Japan
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    • Fax: 81-92-642-6202

  • Akihito Sengoku,

    1. Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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  • Eiji Hirose,

    1. Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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  • Hiroshi Iida,

    1. Laboratory of Zoology, Graduate School of Agriculture, Kyushu University, Higashi-ku, Fukuoka, Japan
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  • Yosaburo Shibata

    1. Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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Abstract

Tight junctions (TJs) create a paracellular permeability barrier to restrict the passage of ions, small solutes, and water. Ameloblasts are enamel-forming cells that sequentially differentiate into preameloblasts, secretory, transition, and ruffle-ended and smooth-ended maturation ameloblasts (RAs and SAs). TJs are located at the proximal and distal ends of ameloblasts. TJs at the distal ends of secretory ameloblasts and RAs are well-developed zonula occludens, but other TJs are moderately developed but incomplete zonula occludens (ZO) or less-developed macula occludens. We herein examined the immunofluorescence localization of TJ proteins, 10 claudin isoforms, occludin, ZO-1, and PAR3, a cell polarity-related protein, in ameloblasts of rat upper incisors. ZO-1 and claudin-1 were detected at both ends of all ameloblasts except for the distal ends of SAs. Claudin-4 and occludin were detected at both ends of transition and maturation ameloblasts except for the distal ends of SAs. PAR3 was detected at the proximal TJs of all ameloblasts and faintly at the distal TJs of early RAs. These results indicate that functional zonula occludens formed at the distal ends of the secretory ameloblasts and RAs consisted of different TJ proteins. Therefore, the distal TJs of secretory ameloblasts and RAs may differentially regulate the paracellular permeability to create a microenvironment suitable for enamel deposition and enamel maturation, respectively. In addition, PAR3 may be principally involved in the formation and maintenance of the proximal, but not distal, TJs. Anat Rec, 291:577–585, 2008. © 2008 Wiley-Liss, Inc.

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