128 EXPRESSIONS OF MOUSE TIGHT JUNCTION MOLECULES IN PLACENTA – CLAUDINS AND OTHER PARACELLULAR TRANSPORT MOLECULES

Abstract

Tight junctions (TJ) are composed of a branching network of sealing strands. Tight junctions regulate paracellular conductance and ionic selectivity. The TJ components include the peripheral protein ZO-1, junctional adhesion molecules (JAM), and integral proteins, such as occludin and claudin. Claudins, a family of proteins, are the most important components in TJ. They establish paracellular transport barriers, which control transportation of molecules within intercellular space. The current study focused on expression of claudin, suggesting claudin as a major working molecule in the paracellular transport system. In order to study the mechanisms and roles of the claudin family, the expression levels of claudin family in various organs should be determined. In this study, we examined expression of the mouse placental claudin family. Pregnant C57/BL6 mice (n = 5) were used in this study, and compared with β-actin, expression of TJ proteins, including Claudin-1 to Claudin-24, JAM-a, Zo-1, and occludin, tricellulin, and MarvelD3 was examined. In the transcription levels, Claudin-1 and -4 proteins were predominantly expressed. Claudin-1 and -4 have been known as a responsive gene for a direct decrease in paracellular conductance by selective reduction of the permeability of Na⁺ ions. On the other hand, Claudin-2, Claudin-3, Claudin-5, Cludin-11, and Claudin-12 showed ~33% expression compared with Claudin-1. Claudin-6 and Claudin-7 showed ~20% relative expression compared to Claudin 1. Claudin-10a and Claudin-16 were not detectable by real-time RT-PCR under our experimental conditions. Other claudin proteins showed low expression. Because the transcriptional levels of TJ genes were expressed variously, protein levels and their localization in the placenta will be further evaluated by immunostaining and Western blot assay. This study will provide data on expression of TJ genes and their localization in the mouse placenta, which may contribute to assuming the roles of these TJ genes regarding maternal-fetal ion transportation in the placenta.