title: Differential expression of claudin-2 along the human intestine: Implication of GATA-4 in the maintenance of claudin-2 in differentiating cells.
abstract: Claudins, and particularly claudin-2, are important regulatory components of tight junction permeability. A better understanding of the involvement of claudin-2 in intestinal barrier functions requires the characterization of its distribution and regulation in the intestine. Interestingly, the claudin-2 gene promoter harbors a number of similarities to that of sucrase-isomaltase, a marker of enterocyte differentiation. We thus investigated the expression of claudin-2 in relation to the transcription factors CDX2, HNF-1alpha, and GATA-4 in the human intestine. The characterization of claudin-2 and the expression of the above transcription factors were performed by immunofluorescence, Western blot, and RT-PCR in the developing human intestinal epithelium. The functional role of CDX2, HNF-1alpha, and GATA-4 on claudin-2 regulation was also examined by ectopic expression studies in intestinal cell models. Claudin-2 was detected in both crypt and villus cells of the small intestine but restricted to undifferentiated crypt cells in the colon. CDX2 and HNF-1alpha were expressed along the entire intestine whereas GATA-4 was undetectable in the colon. Accordingly, in the colonic Caco-2 cell model, claudin-2 was found to be present only in undifferentiated cells. Like in the colonic epithelium, GATA-4 was found to be also lacking in Caco-2 cells while CDX2 and HNF-1alpha were present at significant levels. Cotransfection experiments showed that the claudin-2 promoter was activated by CDX2, HNF-1alpha, and GATA-4 in a cooperative manner. Furthermore, forced GATA-4 expression in Caco-2 cells enhances maintenance of claudin-2 expression during differentiation. These observations suggest that optimal claudin-2 expression in the gut relies on the presence of GATA-4, suggesting a role for this factor in intestinal regionalization.
authors.affiliation: CIHR Group on Functional Development and Physiopathology of the Digestive Tract, Département d'anatomie et de Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Escaffit
authors.forename: F
authors.initials: F
authors.lastname: Boudreau
authors.forename: J-F
authors.initials: JF
authors.lastname: Beaulieu
mesh_terms: D000071616:CDX2 Transcription Factor; D018938:Caco-2 Cells; D002454:Cell Differentiation / Q000502:physiology; D057167:Claudins; D003106:Colon / Q000166:cytology / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D050991:GATA4 Transcription Factor; D005786:Gene Expression Regulation / Q000502:physiology; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D007421:Intestine, Small / Q000166:cytology / Q000502:physiology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D019108:Tight Junctions / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; C491875:CLDN2 protein, human; D057167:Claudins; D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; C496487:HNF1A protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1