Cloning of canine Toll-like receptor 9 and its expression in dog tissues

Toll-like receptor 9 (TLR9) is activated by bacterial DNA and induces production of inflammatory cytokines. In this study, canine TLR9 cDNA was cloned and sequenced. Further, the expression of TLR9 mRNA was investigated in canine tissues. The full-length cDNA for the canine TLR9 gene was 3419 bp encoding 1032 amino acids. The similarity of canine TLR9 with those of cat, cattle, human, mouse and pig was 90, 84.3, 83.6, 76.3 and 85.2% at the nucleotide level, and 90.5, 82.7, 81.4, 74.8 and 85.7% at the amino acid level. By reverse transcription-polymerase chain reaction (RT-PCR) analysis, canine TLR9 mRNA was detected in venous blood mononuclear cells and lymph node and weakly in spleen, whereas it was not detected in kidney, liver, pancreas, lung, small intestine, large intestine, heart, skin, muscle, stomach and bladder.