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.

Interleukin-13 (IL-13)/IL-13 Receptor α1 (IL-13Rα1) Signaling Regulates Intestinal Epithelial Cystic Fibrosis Transmembrane Conductance Regulator Channel-dependent Cl− Secretion

“…Another potential factor that may explain the observed conflicting reports is the different intestinal epithelial cell maturation and differentiation states. Caco2 cells express claudin-2 early following passaging and during proliferation; however, this tight junction protein is subsequently down-regulated during differentiation (54). Consistent with this, Prasad et al (36) observed decreased expression of claudin 2 and increased expression of claudin 3 and 4 over time and importantly demonstrated that these changes correlated with increased intestinal epithelial permeability.…”

Symplekin promotes tumorigenicity by up-regulating claudin-2 expression

“…This protein is known to convert TJ from a tight to a leaky strand phenotype (20), and its expression is regulated by cingulin, another TJ cytoplasmic plaque protein that modulates proliferation in Madin-Darby canine kidney cells (27). The transcriptional regulation of CLDN2 by nuclear symplekin provides a potential explanation for the similarities of their expression pattern in human CRC, where claudin-2 also is overexpressed (23), and in healthy human and rodent colonic epithelia, where claudin-2 expression is restricted to the bottom section of the Lieberkühn crypts (28)(29)(30). In addition, because de novo experimental expression of claudin-2 restores the proliferation and anchorage-independent potential of cells with down-regulated symplekin, we conclude that claudin-2 is an essential mediator in the tumor-promoting role of symplekin.…”

Hepatocyte nuclear factor-4α promotes differentiation of intestinal epithelial cells in a coculture system

“…Total RNA was isolated from cultured cells and subjected to a DNase treatment according to the manufacturer's instructions (Totally RNA kit). Reverse transcriptions were carried out at 42°C for 1 h in the presence of 2 g RNA, 40 mU of polyoligo(dT) [12][13][14][15][16][17][18], and 40 U of Reverse Transcriptase (Roche Diagnostics). Semiquantitative PCR was performed in a total volume of 20 l in the presence of 1 l of RT reaction, 0.6 U of Taq DNA polymerase (New England Biolabs), 0.2 mM dNTPs, and 30 ng of each specific primer.…”

“…Cdx2, an intestinal epithelial specific transcription factor, regulates transcriptional activity of several intestinal epithelial-specific genes [for a review, see Guo et al (17)]. Other transcriptional regulators such as GATA-4 or hepatocyte nuclear factor-1␣ (HNF-1␣) cooperate with Cdx2 and regulate transcription of sucrase-isomaltase (SI) (6), lactase-phlorizin hydrolase (31,56), calbindin 3 (60), liver fatty acid binding protein gene (52), and claudin 2 (13,46). Restriction of apolipoprotein A-IV (ApoA-IV) expression to villus-differentiated enterocytes has been functionally linked to hepatocyte nuclear factor-4␣ (HNF-4␣) (49).…”