Functional adaptive diversity of the Atlantic salmon T-cell receptor gamma locus

The Ad antic salmon (Salmo salar) T-cell receptor gamma(TCR gamma) gene has extensive diversity in its capacity for antigen recognition due to the V-J-C gene segments recombinational possibilities, and N-region diversity. This is the first report completely characterizing and annotating a TCR gamma gene locus in teleosts. We identified two different TCR gamma loci in Atlantic salmon. The first locus, TCR gamma 1, spans 260 kbp and contains four tandemly repeated clusters each of which consists of 1-4 variable (V) segments, 1-2 sets of a joining (J) segment and a constant (C) region. In total, 10 V segments, 5 J segments and 5 C regions were found in locus 1. In the second locus, TCR gamma 2, a single non-expressed V-J-C cluster was found. Surprisingly, the Atlantic salmon TCR gamma loci have a larger number of C regions relative to other teleosts, mouse and human. In addition, each Atlantic salmon TCR gamma C region has a different connecting peptide region that may result in distinct cellular responses. Expression data confirm the diverse repertoire found at the genomic level. At least 6 out of 7 functional V segments, all 5 J segments and all 5 C regions found in TCR gamma I were identified in TC gamma transcription analysis. The identification and characterization of the functional TCR gamma 1 along with the associated TCR alpha/delta locus suggest that Atlantic salmon have a functional -gamma delta T-cell immune component. (C) 2007 Elsevier Ltd. All rights reserved.