Research Note: Junctional adhesion molecule A is expressed in epithelial cells of the crypt and villi whereas junctional adhesion molecule 2 is expressed in vascular cells.

A functional intestinal barrier is essential for a healthy intestine. This barrier includes an apical tight junctional complex between adjacent intestinal epithelial cells. The tight junctions (TJ) are multiprotein junctional complexes that consist of a number of members of the occludin, claudin, zona occludens, and junctional adhesion molecule families. The mRNA expression of junctional adhesin molecule A (JAMA) and junctional adhesion molecule 2 (JAM2) are 2 TJ mRNAs that are often used to assess intestinal barrier integrity. The objective of this study was to use in situ hybridization to identify cells that express JAMA and JAM2 mRNA in the small intestine of chickens. In the jejunum of a 21 d old broiler, JAMA mRNA was highly expressed in the epithelial cells of the villi and crypt. By contrast, JAM2 mRNA was located in the vascular system in the center of the villi and in the lamina propria. These results demonstrate that JAMA and not JAM2 is the appropriate gene to use when assessing TJ between intestinal epithelial cells.