Meeting Abstract
97.1 Wednesday, Jan. 7 Claudin mRNA expression in Mozambique tilapia (Oreochromis mossambicus) gill tissue: implications for osmoregulation and salinity adaptation. BALTZEGAR, David A*; OZDEN, Ozkan; BORSKI, Russell J.; North Carolina State University, Raleigh; North Carolina State University, Raleigh; North Carolina State University, Raleigh dabaltze@ncsu.edu
Claudins, a superfamily of tetra-spanning transmembrane proteins, are major constituents of epithelial tight junctions. Claudins are selectively expressed in different tissues, and the relative amount and composition of these proteins are thought to govern transepithelial resistance by selective ion permeability within the tight junction. In mammals, 24 claudins have been reported. A putative genome duplication event has led to a large expansion of claudin genes within the teleost lineage, with 56 claudins reported in the Japanese puffer. These claudins may function in hydromineral balance in teleosts by governing the paracellular ion transport properties of gill epithelia. Claudin regulation during salinity adaptation in fish is still not well understood. We have cloned and characterized three claudin genes: Cldn3c, Cldn28a, and Cldn30 in the Mozambique tilapia (Oreochromis mossambicus). Maximum likelihood phylogenetic analyses of tilapia Cldn28a and Cldn30 suggest distant homology to mammalian Cldn4, while Cldn3c is related to mammalian Cldn3. We found that the mRNAs of these claudins were expressed in a tissue-specific distribution profile in freshwater (FW; 0-2 ppt) and seawater (2/3 SW; 25 ppt) fish. Expression of these genes is most abundant in gill and skin, with Cldn30 and Cldn3c also showing significant abundance in posterior intestine. In the gill, Cldn3c expression is significantly lower in seawater fish (p < 0.001) compared to freshwater fish. Cldn28a and Cldn30 expression did not vary between long-term acclimated fish. Along with our previous studies, these results suggest that multiple claudins may be important in salinity acclimation in tilapia.
