Cloning, expression and bioinformatics analysis of the duck TLR 4 gene.

1. Toll-like receptors (TLRs) are type I transmembrane proteins that play an essential role in the innate immune system. Studies on the structure and function of TLRs can be applied to the development of new approaches to control diseases of humans and animals. 2. A 3432-bp cDNA encoding duck toll-like receptor 4 (duTLR4) was cloned from duck splenic lymphocytes using RT-PCR and rapid amplification of cDNA ends. 3. The encoded protein, which was predicted to contain 843 amino acids, had a molecular weight of 96·01 kDa and included an archetypal toll/interleukin-1 receptor domain, a transmembrane domain, and a distinctive arrangement of extracellular leucine-rich repeat regions similar to chicken TLR4, human TLR4, and mouse TLR4. The duTLR4 showed 82·1% amino acid sequence identity with previously described chicken TLR4, and 43·2-45·2% sequence identity with mammalian homologs. 4. RT-qPCR analysis indicated that the duTLR4 gene was strongly expressed in the liver, kidney, spleen, intestine, and brain.