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Mammalian occludin in epithelial cells: its expression and subcellular distribution
M Saitou1, Y Ando-Akatsuka, M Itoh
1Department of Cell Biology, Faculty of Medicine, Kyoto University, Japan.
European Journal of Cell Biology
|July 1, 1997
Summary
Mammalian occludin, a novel tight junction protein, is expressed in various epithelial tissues. Its localization and expression patterns correlate with tight junction development, distinguishing it from ZO-1.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Occludin is a novel integral membrane protein found at tight junctions.
- Mammalian occludin cDNA was recently identified, prompting further investigation.
- Tight junctions are crucial for epithelial cell barrier function.
Purpose of the Study:
- To characterize the basic properties of mammalian occludin at the DNA, RNA, and protein levels.
- To investigate the expression patterns and localization of occludin in epithelial cells.
- To compare occludin's tight junction specificity with that of ZO-1.
Main Methods:
- Fluorescent in situ hybridization for gene mapping.
- Northern blotting for mRNA analysis.
- Production of antibodies for protein detection via Western blotting and immunofluorescence microscopy.
- Immunoreplica electron microscopy for precise localization.
Main Results:
- The human occludin gene was mapped to chromosome 5q13.1.
- Multiple occludin mRNA transcripts were detected, suggesting alternative splicing.
- Occludin mRNA was found in epithelial cells and specific organs (testis, kidney, liver, lung, brain), but not fibroblasts.
- Antibodies recognized occludin in multiple species, localizing it to ~60 kDa bands in epithelial cells.
- Occludin staining intensity correlated with tight junction strand number, unlike ZO-1 staining.
Conclusions:
- Mammalian occludin is a specific marker for tight junctions in epithelial cells.
- Occludin's expression and localization are consistent with its role in tight junction formation and function.
- Occludin provides a more specific marker for tight junctions compared to ZO-1.