Figure 4.

Dβ gene segments are frequently deleted in cR2 mice as compared with WT mice. (A) Diagram of a portion of the TCRβ locus showing the Dβ2 gene segment in its germline configuration (upper) and after a deletion event (lower). Horizontal arrows indicate the relative positions of a set of PCR primers that amplify the Dβ gene segment from HaeIII-restricted genomic DNA from either cR2 or WT thymus. (B) Negative image of agarose gel analysis of amplification products obtained from thymic DNA purified from six individual mice of the indicated genotypes (lanes 1–6) along with negative controls [reactions programmed with either DNA from 63-12, a RAG2-null cell line (lane 7) or H₂0 (lane 8)]. (C) The three cR2 PCR products (minus, lanes 1, 3 and 5) were restricted with ApaLI (plus, lanes 2, 4 and 6) which cleaves perfect signal joint sequences (GTG/CAC) remaining after deletion of the Dβ2 coding segment, releasing the expected fragments [341 and 106 bp (not visible)]. Sequence analysis of the PCR products further confirmed their nature (Supplementary Table S3).