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Tissue expression of claudin-1 and claudin-2 tight junction proteins in chickens

Stewart, Sydney
Robinson, Kelsy
Understanding gut homeostasis is an active area of research in livestock animals, as it is key to improving animal health and efficiency. Tight junction proteins are responsible for preventing the transport of foreign materials and microorganisms between cells in epithelial and endothelial tissue layers while also regulating the passage of water and ions. Their location and function within these protective barrier tissues suggest that tight junction proteins play a significant role in the tissue integrity and innate immunity of the host. The purpose of this study is to examine the expression patterns of mRNAs for different tight junction proteins in various tissues of broiler chickens. Tissue samples were collected from four 30-day old, healthy broiler chickens raised under standard care. Total RNA was isolated, reverse transcribed, and quantitative polymerase chain reaction (qPCR) was performed to measure the mRNA expressions of two major tight junction proteins, namely claudin-1 and claudin-2, in the skin, brain, lung, and various segments of the digestive tract. Fold differences among tissue types was calculated using the Ct method normalized to the expression of a house-keeping gene, GAPDH. Our results indicated that claudin-1 mRNA was abundant in the skin, lung, spleen, and pancreas, with approximately 250-, 300-, 200-, and 150-fold higher than the brain, respectively. Meanwhile, claudin-2 mRNA was highly expressed in the duodenum, spleen, and pancreas, showing approximately 900-, 650-, and 700-fold higher than the brain, respectively. Understanding the tissue expression patterns of major tight junction proteins represent an important first step in identifying the strategies to modulate their expression in the intestinal tract, thereby improving gut health, immunity, and production efficiency of chickens.