Alternative splicing restricts translation of rearrangements at the T-cell receptor delta/alpha locus

Lymphocytes expressing alpha beta or gamma delta T-cell receptors (TCR) represent distinct T-cell populations. Because TCR delta genes lie within the TCR alpha locus, the rearrangement processes, transcription, and translation of TCR delta or TCR alpha variable domain exons require tight regulation. Human precursor B-cell leukemias (eg, the REH cell line) constitute an interesting model to study TCR delta/alpha recombination because they rearrange TCR delta/alpha loci along a hierarchically ordered pathway in which V delta 2D delta 3 segments are joined to the J alpha cluster. We now show for REH cells that chimeric TCR delta/alpha variable domain exons are posttranscriptionally modified by alternative splicing resulting in truncated V delta 2C alpha transcripts. This process also takes place during thymic differentiation. CD7+/CD3- T-cell precursors exhibit V delta 2D delta 3 rearrangements. Further differentiation into CD7+/CD3+ thymocytes is associated with the expression of a truncated V delta 2C alpha RNA species. In contrast, chimeric TCR delta/alpha rearrangements containing a V delta 1 segment (but no D delta sequences) are predominantly expressed as full-length V delta 1J alpha C alpha transcripts. These data suggest that alternative splicing constitutes a mechanism that restricts the production of distinct chimeric TCR alpha chains.