Cloning and expression of a mouse member of the PLUNC protein family exclusively expressed in tongue epithelium

Palate, lung, and nasal epithelium clone (Plunc, now renamed Splunc1) is a small secreted protein expressed in the oropharynx and upper airways of humans, mice, rats, and cows. This protein is structurally homologous to known mediators of host defense against gram-negative bacteria. We have characterized the genomic sequence and expression of a novel but closely related gene from rodents, which we call splunc5. Mouse Splunc5 sequence is 60% identical to mouse Splunc1. The genes also share highly conserved genomic elements including intron–exon structure and intronic sequence. Strikingly, splunc5 is expressed exclusively in the interpapillary epithelium of the tongue's dorsal surface. By comparing the expression profiles of splunc5, splunc1, and a third related sequence, lplunc1, in mice, we show that these genes are expressed in unique domains along a continuous corridor of oral, lingual, pharyngeal, and respiratory epithelia. This expression pattern is consistent with the hypothesis that these proteins protect epithelial surfaces colonized by potentially pathogenic microorganisms.