Gene expression pattern analysis of the tight junction protein, Claudin, in the early morphogenesis of Xenopus embryos
ABSTRACT To study how epithelial layers are formed during early development in Xenopus embryos, we have focused on Claudin, the major component of the tight junction. So far, 19 claudin genes have been found in the mouse, expressed in different epithelial tissues. However, though a number of cytological studies have been done for the roles of Claudins, their expression patterns and functions during early embryogenesis are largely unknown. We found three novel Xenopus claudin genes, which are referred to as claudin-4L1, -4L2, and -7L1. At the early gastrula stage, claudin-4L1, -4L2, and -7L1 mRNAs were detected in the ectoderm and in the mesoderm. At the late gastrula stage, claudin mRNAs were detected in the ectoderm through the involuting archenteron roof. At the neurula stage, claudin-4L1/4L2 and -7L1 mRNAs were differentially expressed in the neural groove and the epidermal ectoderm. At the tailbud stage, the claudin mRNAs were found in the branchial arches, the otic vesicles, the sensorial layer of the epidermis, and along the dorsal midline of the neural tube. In addition, claudin-4L1/4L2 mRNAs were detected in the pronephros and the endoderm, whereas claudin-7L1 mRNA was observed in the epithelial layer of the epidermis.
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ABSTRACT: In vertebrates, the positioning of the internal organs relative to the midline is asymmetric and evolutionarily conserved. A number of molecules have been shown to play critical roles in left-right patterning. Using representational difference analysis to identify genes that are differentially expressed on the left and right sides of the chick embryo, we cloned chick Claudin-1, an integral component of epithelial tight junctions. Here, we demonstrate that retroviral overexpression of Claudin-1, but not Claudin-3, on the right side of the chick embryo between HH stages 4 and 7 randomizes the direction of heart looping. This effect was not observed when Claudin-1 was overexpressed on the left side of the embryo. A small, but reproducible, induction of Nodal expression in the perinodal region on the right side of the embryo was noted in embryos that were injected with Claudin-1 retroviral particles on their right sides. However, no changes in Lefty,Pitx2 or cSnR expression were observed. In addition, Flectin expression remained higher in the left dorsal mesocardial folds of embryos with leftwardly looped hearts resulting from Claudin-1 overexpression on the right side of the embryo. We demonstrated that Claudin-1's C-terminal cytoplasmic tail is essential for this effect: mutation of a PKC phosphorylation site in the Claudin-1 C-terminal cytoplasmic domain at threonine-206 eliminates Claudin-1's ability to randomize the direction of heart looping. Taken together, our data provide evidence that appropriate expression of the tight junction protein Claudin-1 is required for normal heart looping and suggest that phosphorylation of its cytoplasmic tail is responsible for mediating this function.Mechanisms of Development 04/2006; 123(3):210-27. DOI:10.1016/j.mod.2005.12.004 · 2.24 Impact Factor
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ABSTRACT: Claudins are membrane proteins located within tight junctions. Using degenerate and gene specific primers the chick homologue of Claudin-3 was isolated. Here we show the expression of Claudin-3 transcripts in the developing chick embryo from Hamburger and Hamilton Stages (HH) 6-22. The early expression domains of Claudin 3 in the developing chick embryo include the mesoderm surrounding Hensen's node and the head fold. Between HH 9 and HH 11 expression domains include the anterior intestinal portal and otic vesicle. By HH 14, gene expression is observed in the pharyngeal endoderm and pouches, in addition to the continued expression in the otic vesicle. Expression in the more posterior pouches was also observed as development proceeded. At HH 20 expression is present in the mesonephric system and also the developing liver, lung bud and intestine.Gene Expression Patterns 01/2006; 6(1):40-4. DOI:10.1016/j.modgep.2005.05.002 · 1.36 Impact Factor
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ABSTRACT: The interaction of the Eph family of receptor protein tyrosine kinase and its ligand ephrin family induces bidirectional signaling via the cell-cell contacts. Although most previous studies have focused on the function of Eph-ephrin pathways in the neural system and endothelial cells, this process also occurs in epithelial and cancer cells, of which the biological involvement is poorly understood. We show that ephrin-B1 creates an in vivo complex with adjacent claudin1 or claudin4 via the extracellular domains of these proteins. The cytoplasmic domain of ephrin-B1 was phosphorylated on tyrosine residues upon the formation of cell-cell contacts, possibly recognizing an intercellular adhesion of claudins. Phosphorylation of ephrin-B1 induced by claudins was abolished by the treatment with 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, an inhibitor of the Src family kinases. Moreover, overexpression of ephrin-B1 triggered consequent change in the level of cell-cell adhesion depending on its phosphorylation. These results suggest that ephrin-B1 mediated the cell-cell adhesion of epithelial and cancer cells via a novel Eph receptor-independent mechanism.The EMBO Journal 12/2005; 24(21):3700-11. DOI:10.1038/sj.emboj.7600831 · 10.75 Impact Factor