Consensus phylogenetic tree of claudin proteins. The trees were generated using 109 claudin protein sequences from human (hu, yellow), mouse (mu, red), Fugu (fu, green), and zebrafish (zf, blue) and using a related gene from Ciona (ci) as an outgroup gene. To reduce the complexity of phylogenetic trees, claudin genes were first divided into two groups of related proteins based on the results of preliminary phylogenetic analysis, and phylogenetic trees were generated separately for the two groups. Based on the origin and phylogenetic relationships, vertebrate claudin genes were classified into nine classes (A, Class I–III; B, Class IV–IX). Bootstrap values >50% are given.
