title: Differential expression of the tight junction proteins, claudin-1, claudin-4, occludin, ZO-1, and PAR3, in the ameloblasts of rat upper incisors.
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.
authors.affiliation: Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan. inai@ana2.med.kyushu-u.ac.jp
authors.forename: Tetsuichiro
authors.initials: T
authors.lastname: Inai
authors.forename: Akihito
authors.initials: A
authors.lastname: Sengoku
authors.forename: Eiji
authors.initials: E
authors.lastname: Hirose
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iida
authors.forename: Yosaburo
authors.initials: Y
authors.lastname: Shibata
mesh_terms: D000565:Ameloblasts / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D062445:Claudin-1; D062506:Claudin-4; D007180:Incisor / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D019108:Tight Junctions / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: D002352:Carrier Proteins; D062445:Claudin-1; D062506:Claudin-4; C568114:Cldn1 protein, rat; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D062793:Occludin; C568987:Ocln protein, rat; C472451:Pard3 protein, rat; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein