Comparative analysis of the chicken TCRα/δ locus

The access to whole genome sequences has provided the opportunity to study the evolution and organization of immunologically related genes on a large scale. The genes encoding the T cell receptor (TCR) alpha and delta chains are part of a complex locus that has shown remarkable conserved organization across different amniote lineages. In this study we have examined and annotated the TCR alpha/delta locus in chicken (Gallus gallus) and compared it to that of zebra finch (Taeniopygia guttata) and other avian species using the current available genome data. We also analyzed the expressed chicken TCR alpha/delta transcript repertoire and compared it with that previously described for zebra finch. The analyses conducted in this study show that the TCR alpha/delta locus in birds has undergone major rearrangements and expansion of the germ line repertoire in chicken, compared to zebra finch. A major expansion of the chicken variable gene repertoire appears to be driven by selection for genes from a limited number of subgroups.