Trav15-dv6 family Tcrd rearrangements diversify the Tcra repertoire

The Tcra repertoire is generated by multiple rounds of V(α)-J(α) rearrangement. However, Tcrd recombination precedes Tcra recombination within the complex Tcra-Tcrd locus. Here, by ablating Tcrd recombination, we report that Tcrd rearrangement broadens primary V(α) use to diversify the Tcra repertoire in mice. We reveal that use of Trav15-dv6 family V gene segments in Tcrd recombination imparts diversity in the Tcra repertoire by instigating use of central and distal V(α) segments. Moreover, disruption of the regions containing these genes and their cis-regulatory elements identifies the Trav15-dv6 family as being responsible for driving central and distal V(α) recombinations beyond their roles as substrates for Tcrd recombination. Our study demonstrates an indispensable role for Tcrd recombination in general, and the Trav15-dv6 family in particular, in the generation of a combinatorially diverse Tcra repertoire.