INTERSPECIES DIVERSITY OF THE OCCLUDIN SEQUENCE - CDNA CLONING OF HUMAN, MOUSE, DOG, AND RAT-KANGAROO HOMOLOGS

Occludin has been identified from chick liver as a novel integral memb rane protein localizing at tight junctions (Furuse, M., T. Hirase, M. Itoh, A. Nagafuchi, S. Yonemura, Sa. Tsukita, and Sh. Tsukita. 1993. J . Cell Biol. 123:1777-1788). To analyze and modulate the functions of tight junctions, it would be advantageous to know the mammalian homolo gues of occludin and their genes. Here we describe the nucleotide sequ ences of full length cDNAs encoding occludin of rat-kangaroo (potoroo) , human, mouse, and dog. Rat-kangaroo occludin cDNA was prepared from RNA isolated from PtK2 cell culture, using a mAb against chicken occlu din, whereas the others were amplified by polymerase chain reaction ba sed on the sequence found around the human neuronal apoptosis inhibito ry protein gene. The amino acid sequences of the three mammalian (huma n, murine, and canine) occludins were very closely related to each oth er (similar to 90% identity), whereas they diverged considerably from those of chicken and rat-kangaroo (similar to 50% identity). Implicati ons of these data and novel experimental options in cell biological re search are discussed.