Assembly of productive T cell receptor delta variable region genes exhibits allelic inclusion

Abstract

The generation of a productive "in-frame" T cell receptor beta (TCR beta), immunoglobulin (Ig) heavy (H) or Ig light (L) chain variable region gene can result in the cessation of rearrangement of the alternate allele, a process referred to as allelic exclusion. This process ensures that most alphabeta T cells express a single TCR beta chain and most B cells express single IgH and IgL chains. Assembly of TCR alpha and TCR gamma chain variable region genes exhibit allelic inclusion and alphabeta and gammadelta T cells can express two TCR alpha or TCR gamma chains, respectively. However, it was not known whether assembly of TCR delta variable regions genes is regulated in the context of allelic exclusion. To address this issue, we have analyzed TCR delta rearrangements in a panel of mouse splenic gammadelta T cell hybridomas. We find that, similar to TCR alpha and gamma variable region genes, assembly of TCR delta variable region genes exhibits properties of allelic inclusion. These findings are discussed in the context of gammadelta T cell development and regulation of rearrangement of TCR delta genes.

Figure 1

Schematic of the mouse TCR α/δ locus. Shown are the Vα/Vδ gene segments, the Dδ and Jδ gene segments, the TCR δ enhancer (Eδ), the TCR δ constant region gene (Cδ), and the Vδ5 gene segment. This is followed by the Jα gene segments, the TCR α constant region gene (Cα), and the TCR α enhancer (Eα). Also shown are probes 1 and 3 through 6 and the approximate position of the BglII (B2) sites. The schematic is not drawn to scale.

Figure 2

Analysis for the presence of the CBA and C57BL6 TCR δ alleles. Genomic DNA from the hybridoma fusion partner BW 1100.129.237 (BW), CBA kidney (CBA), C57BL6 kidney (B6), or γδ T cell hybridomas (F1D) was digested with HindIII and subjected to Southern blot analysis using probe 6 (Fig. 1). The 2-kb marker is shown.

Figure 3

Analysis of rearrangements to Jδ1 and Jδ2. Genomic DNA samples described in the legend to Fig. 1 were digested with either BglII (a) or HindIII (b) and subjected to Southern blot analysis using probes 1, 3, and 4 (a) or probe 5 (b). Shown are the 9-, 6- and 4-kb molecular mass markers.

Figure 3

Analysis of rearrangements to Jδ1 and Jδ2. Genomic DNA samples described in the legend to Fig. 1 were digested with either BglII (a) or HindIII (b) and subjected to Southern blot analysis using probes 1, 3, and 4 (a) or probe 5 (b). Shown are the 9-, 6- and 4-kb molecular mass markers.