Location: Warmwater Aquaculture Research UnitTitle: Comprehensive survey and genomic characterization of toll-like receptors in channel catfish, Ictalurus punctatus: identification of novel fish TLRs Author
Submitted to: Immunogenetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2013
Publication Date: 7/1/2013
Citation: Quiniou, S., Boudinot, P., Bengten, E. 2013. Comprehensive survey and genomic characterization of toll-like receptors in channel catfish, Ictalurus punctatus: identification of novel fish TLRs. Immunogenetics. 65(7):511-530. Interpretive Summary: Diseases are responsible for significant economical loss to the aquaculture industry. Toll receptor molecules specialize in early detection of pathogens (bacteria, virus, parasites) and as such are at the forefront of the fight against pathogens. In this study, we characterized a comprehensive set of toll receptors in channel catfish. This information will help us understand how catfish fight their pathogens, optimize vaccines to trigger an effective immune response or select catfish with the best genotypes for pathogen detection in order to improve health performance.
Technical Abstract: A comprehensive survey of channel catfish Toll-Like Receptors (TLRs) was undertaken following a genomic PCR approach based on degenerate primers. Twenty different TLRs were identified in channel catfish. Channel catfish TLR sequences were characterized by phylogenetic analysis based on their conserved Toll/Interleukin-1 Receptor (TIR) domain and by in depth analysis of Leucine Rich Repeat (LRR) motifs of the ligand binding Extra Cellular Domain (ECD). The catfish have representatives of all the TLR types defined in vertebrates with the exception of 6, 10, 11, 12, 13, 15, 23 and 24. Additionally two new types were discovered TLR 25 and TLR 26. TLR25 is also present in cyprinids, cichlids, plecoglossids, and adrianichthyids suggesting its presence early in fish evolution. To date, TLR26 was found only in channel catfish. Like TLR18-23, TLR 25 and 26 were not found in any other vertebrate classes and appear to be fish specific. Data mining using the catfish TLR sequences revealed that in addition to ictalurids and cyprinids TLR4 is also present in salmonids. TLR19 and TLR20 were both found in ictalurids, cyprinids and salmonids, demonstrating a wider range than previously known. The LRR structure within ECDs appeared generally well conserved. TLR 7 demonstrated a very high identity to human TLR7 strongly suggesting that ligand specificity maybe conserved. Finally, expression profiling confirmed that most TLR are widely expressed in a diversity of tissues, and revealed marked differences of expression level.