Expression of Claudin Tight Junction Proteins in Response to Varying Environmental and Physiological Conditions.

Abstract

In this study, the localization and possible functions of claudin tight junction proteins in bird and fish gastrointestinal tract were investigated. Claudin expression was detected in the chick intestine during the last week of embryonic development using microarrays and quantitative real time PCR analyses. Expression profiles differed among the claudins suggesting that they might play different roles in the establishment of intestinal tight junctions during embryonic development. Glucocorticoids are essential for the maturation of numerous tissues during embryonic development and are known to increase the integrity of tight junctions. This study reveals that treatment of 18-day old embryonic intestine with the synthetic glucocorticoid dexamethasone elevates mRNA levels of two claudins within 12 hours. Expression profiles of claudins were also analyzed in the gastrointestinal tract of Mozambique Tilapia. Immunohistochemistry and real-time PCR analyses revealed that various claudins were expressed in the tilapia gut in a tissue specific manner. Salinity transfer experiments indicated that salinity differentially regulates the expression of certain claudins suggesting a role for these proteins in osmoregulation.