In every jawed vertebrate species studied so far, the T cell receptor (TCR) complex is composed of two different TCR chains (α/β or γ/δ) and a number of CD3 subunits responsible for transmitting signals into the T cell. In this study, we characterised all of the TCR and CD3 genes of small-spotted catshark (Scyliorhinus canicula) and analysed their expression in a broad range of tissues. While the TCR complex is highly conserved across jawed vertebrates, we identified a number of differences in catshark, most notably the presence of two copies of both TCRβ and CD3γδ, and the absence of a functionally-important proline rich region from CD3ε. We also demonstrate that TCRβ has duplicated independently multiple times in jawed vertebrate evolution, bringing additional diversity to the TCR complex. This study reveals new insights about the evolutionary history of the TCR complex and raises new avenues for future exploration.
This work was supported by a PhD studentship awarded by the University of Aberdeen, College of Life Sciences and Medicine to RP, and a Royal Society research grant [RG130789] awarded to HD. The authors thank Kathryn Crouch for providing the nurse shark transcriptome assembly, Milena Monte, Kimberley Mackenzie, Heather Ritchie and Abdullah Alzaid for technical advice, and Marianna Chimienti for help with manuscript editing.
- T cell receptor
- Cartilaginous fish