By using the combination of reverse-transcription PCR and rapid amplification of cDNA ends methods, a cDNA encoding mast cell tryptase was successfully cloned from the small intestine of Mongolian gerbil, Meriones unguiculatus, infected with Nippostrongylus brasiliensis. The cDNA was 1219 bp long including 810 bp of an open reading frame. Based on the deduced amino acid sequences of known mast cell tryptases of other species, the gerbil mast cell tryptase (gMCT) was highly similar to mouse mast cell protease (mMCP)-7, and seems to be translated as a prepro-enzyme with 25 amino acids of signal and activation peptides and 245 amino acids of mature enzyme. The gMCT mRNA was preferentially transcribed in the intestinal mucosa and to a far lesser extent in the connective tissue such as skin and tongue. Moreover, kinetic study after infection revealed that the amount of gMCT mRNA in the small intestine correlated well with the degree of intestinal mastocytosis. Throughout the course of infection, enzyme-histochemically detectable tryptase activity was limited to mucosal mast cells. Since mucosal mast cells of other rodents, including mice and rats, do not express tryptases, this is the first report of rodent mast cell tryptase expressed in the intestinal mucosa.

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