Expression of Claudin-3 during chick development.

Claudins are membrane proteins located within tight junctions. Using degenerate and gene specific primers the chick homologue of Claudin-3 was isolated. Here we show the expression of Claudin-3 transcripts in the developing chick embryo from Hamburger and Hamilton Stages (HH) 6-22. The early expression domains of Claudin 3 in the developing chick embryo include the mesoderm surrounding Hensen's node and the head fold. Between HH 9 and HH 11 expression domains include the anterior intestinal portal and otic vesicle. By HH 14, gene expression is observed in the pharyngeal endoderm and pouches, in addition to the continued expression in the otic vesicle. Expression in the more posterior pouches was also observed as development proceeded. At HH 20 expression is present in the mesonephric system and also the developing liver, lung bud and intestine.