Location: Warmwater Aquaculture Research UnitTitle: Identification and characterization of TCRgamma and TCRdelta chains in channel catfish, Ictalurus punctatus) Author
Submitted to: Immunogenetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2014
Publication Date: 10/1/2014
Citation: Moulana, M., Taylor, E., Edholm, E., Quiniou, S., Wilson, M., Bengten, E. 2014. Identification and characterization of TCRgamma and TCRdelta chains in channel catfish, Ictalurus punctatus. Immunogenetics. 66(9-10):545-561. Interpretive Summary: T cell receptors (TR) are critical elements of the immune response to pathogens. As in mammals, two type of T cells are found in fish, expressing either a aß TR or delta TR. The delta TR is not well described in fish. In this study, the gene expression of both the gamma TR gene and the delta TR was characterized in channel catfish by DNA sequencing. Structurally those genes were shown to exhibit conserved architectural motifs and peptides fundamental for their known biological functions in catfish. As a major component of immunity, this information will help understand mechanisms involved in disease resistance in fish.
Technical Abstract: Channel catfish, Ictalurus punctatus, T cell receptors (TCR) gamma and delta were identified by mining of expressed sequence tag databases and full length sequences were obtained by 5'-RACE and RT-PCR protocols. cDNAs for each of these TCR chains encode typical variable (V), (diversity; D), joining (J) and constant (C) regions. Three V gamma families, seven J gamma sequences, and three C gamma sequences were identified from sequencing of cDNA. Primer walking on Bacterial Artificial Chromosomes (BACs) confirmed that the TRG locus contained seven TRGJ segments and indicated that the locus consists of (Vgamma3-Jgamma6-Cgamma2) - (Vgamma1n-Jgamma7-Cgamma3) - (Vgamma2-Jgamma5-Jgamma4-Jgamma3-Jgamma2-Jgamma1-Cgamma1). In comparison for TCR delta, two V delta families, four TRDD sequences, one TRJ sequence, and one TRDC sequence were identified by cDNA sequencing. Importantly, the finding that some catfish TCR delta cDNAs contain TCR Valpha-D-Jdelta rearrangements and some TCR alpha cDNAs contain Vdelta-Jalpha rearrangements strongly implies that the catfish TRA and TRD loci are linked. Finally, primer walking on BACs and Southern blotting suggest that catfish have four TRDD gene segments and a single TRDJ and TRDC gene. As in most vertebrates, all three reading frames of each of the catfish TRDD segments can be used in functional rearrangements, and more than one TRDD segment can be used in a single rearrangement. As expected catfish TCR delta CDR3 regions are longer and more diverse than TCR gamma CDR3 regions, and as a group they utilize more nucleotide additions and contain more nucleotide deletions than catfish TCR gamma rearrangements.