Tight junction-related protein expression and distribution in human corneal epithelium.
OBJECTIVE
To investigate the expression and cellular distribution of the tight junction-related proteins occludin, claudin and ZO-1 in human corneal epithelium.


METHODS
Light and electron immunohistochemistry was used to determine tissue distribution of occludin, claudin-1 and ZO-1 in the human corneal epithelium. Reverse transcription-polymerase chain reaction was used to reveal claudin mRNA expression in human corneal epithelium.


RESULTS
In transverse sections, occludin and ZO-1 were localized at the apical cell-cell junctions between superficial cells in stratified corneal epithelium. Both basal and basolateral membranes of superficial cells were stained by the claudin-1 antibody, but no apical membrane staining was observed. In en face sections, claudin-1 and ZO-1 antibodies showed as bands that corresponded to the junctional complex. Claudin-1 staining of superficial cell cytoplasm was also observed. Occludin staining was seen at the junctional complex, where it was not continuous, but dotted along the cell junctions. The transcripts for claudin-1 and several other claudin isotypes, such as -2, -3, -4, -7, -9 and -14 were identified.


CONCLUSIONS
Not only occludin, but also some claudins act as integral transmembrane proteins in the corneal epithelium. ZO-1 is a component of the corneal epithelial tight junction, as it is in most epithelial cells.
Department of Ophthalmology, Nantan General Hospital, 25 Yagiueno, Yagi-cho, Funai-gun, 629-0197, Kyoto, Japan. yban@ophth.kpu-m.ac.jp
Yuriko
Y
Ban
Atsuyoshi
A
Dota
Leanne J
LJ
Cooper
Nigel J
NJ
Fullwood
Takahiro
T
Nakamura
Masakatsu
M
Tsuzuki
Chikako
C
Mochida
Shigeru
S
Kinoshita
D062445:Claudin-1; D019573:Epithelium, Corneal / Q000737:chemistry*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics; D016253:Microscopy, Immunoelectron / Q000379:methods; D062793:Occludin; D010750:Phosphoproteins / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019108:Tight Junctions / Q000737:chemistry*; D062826:Zonula Occludens-1 Protein
C568108:CLDN1 protein, human; D062445:Claudin-1; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; D012333:RNA, Messenger; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein