Toll-like receptors (TLRs) trigger the innate immune system by responding to specific components of microorganisms. MyD88 and TRIF are Toll/interleukin (IL)-1 (TIR)-domain containing adapters, which play essential roles in TLR-mediated signalling via the MyD88-dependant and -independent pathways, respectively. Genes encoding several TLRs have been identified in the chicken genome, however, elements of their signalling pathways have not been well characterized. Here we describe the cloning of chicken MyD88 and TRIF orthologs, and examine the spatial and temporal expression of these genes. The chicken MyD88 cDNA was shown to have an open reading frame (ORF) of 1104 bp, encoding a predicted protein sequence of 368 aa, 8 aa short of a previously published coding sequence due to a premature stop codon. MyD88 gene expression was detected in each tissue tested except in muscle. The chicken TRIF cDNA possessed an ORF of 2205 bp, encoding a predicted protein sequence of 735 aa, which shared 37.3% similarity and 28.9% identity to human TRIF protein sequence. TRIF was ubiquitously expressed in all tissues.

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