Characterization of the zebrafish T cell receptor β locus

Zebrafish (Danio rerio) has become an increasingly important model for immunological study. Its immune system is remarkably similar to that of mammals and includes both the adaptive and innate branches. Zebrafish T cells express functional T cell receptors (TCR), and all four TCR loci are present within the genome. Using 5′-rapid amplification of cDNA ends, we cloned and sequenced zebrafish TCRβ transcripts. TCRβ VDJ coding joints demonstrate conservation of mechanisms used by other vertebrate species to increase junctional diversity. Using the sequences obtained, along with previously published data, we comprehensively annotated the zebrafish TCRβ locus. Overall, organization of the locus resembles that seen in mammals. There are 51 V segments, a single D segment, 27 Jβ1 segments, a single Jβ2 segment, and two constant regions. This description of the zebrafish TCRβ locus has the potential to enhance immunological research in zebrafish and further our understanding of mammalian TCR repertoire generation.