Expression and phylogeny of claudins in vertebrate primordia

Abstract

Claudins, the major transmembrane proteins of tight junctions, are members of the tetraspanin superfamily of proteins that mediate cellular adhesion and migration. Their functional importance is demonstrated by mutations in claudin genes that eliminate tight junctions in myelin and the testis, abolish Mg 2؉ resorption in the kidney, and cause autosomal recessive deafness. Here we report that two paralogs among 15 claudin genes in the zebrafish, Danio rerio, are expressed in the otic and lateral-line placodes at their earliest stages of development. Related claudins in amphibians and mammals are expressed in a similar manner in vertebrate primordia such as sensory placodes, branchial arches, and limb buds. We also show that the claudin gene family may have expanded along the chordate stem lineage from urochordates to gnathostomes, in parallel with the elaboration of vertebrate characters. We propose that tight junctions not only form barriers in mature epithelia, but also participate in vertebrate morphogenesis.

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“…The palcode invaginates and forms a lumen (otic vesicle) at about 18 hpf (42). Cells in the otic vesicle can be labeled by the expression of claudin-a, which is a major transmembrane protein in tight junctions and is specifically expressed in otic vesicle (46). As shown in Fig.…”

Claudins in Normal and Lung Cancer State

“…When the septate junctions (the corresponding structure of invertebrates), were replaced by tight junctions. In the same way as other groups of genes were extended, the claudins diversified into the body of vertebrates from the chordates, leading to new structures: the skull, pairs of sense organs and appendages (Kollmar, et al, 2001). The search for claudins in the Genebank of Drosophyla melanogaster and Caenorhabditis elegans showed no similarity to genes previously reported (Venter & Adams, 2001;Kolmar, et al, 2001).…”

“…The mechanism by which the family of claudins evolves is unknown; however, the data suggest that this family expanded by gene duplication early in the evolution of chordates www.intechopen.com (for review sees: Lal-Nag & Morin 2009, Loh, et al, 2004, Kollmar, et al, 2001. When the septate junctions (the corresponding structure of invertebrates), were replaced by tight junctions.…”

“…In Danio rerio (Zebra fish) have been located at least 15 genes for Cldns, some of which have their orthologous in human (Kollmar, et al, 2001), and among non-vertebrate Halocynthia roretzi (Sea pineapple) as also found a gene that encodes to claudins (Kollmar, et al, 2001). The presence of these genes suggests that the origin of the claudins may be quite ancient and that a claudin ancestor pre-dates the establishment of the chordates (Kollmar, et al, 2001). …”

Signal Transduction Pathways in use of Dexamethasone Implant in the Eye

“…They are responsible for the movements of small molecules and ions, which are characteristic of these tight junction complexes. Numerous claudins form tight junction complexes with different characteristics in different tissues [109,110].…”