Specific transcription of the unrearranged TCR Vβ8.2 gene in lymphoid tissues occurs independently of V(D)J rearrangement

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Abstract
A truncated T cell receptor (TCR) V8.2 polypeptide expressed on the surface of a precursor lymphoid cell line and on a subset of mesenteric lymph node cells has previously been shown to be encoded by transcripts from unrearranged V8 genes. Germline V8 transcription has now been demonstrated in multiple lymphoid and non-lymphoid tissues in mice of varying ages and in cultured cell lines by reverse transcription polymerase chain reaction (RT-PCR). Significant levels of V8 germline transcription were found in thymus. spleen, liver and bone marrow and in all lymphoid cell lines studied. Germline V8 transcription in the liver dropped as mice aged, and increased in the bone marrow. Germline V8 transcription was also detectable in thymus, spleen, liver and bone marrow RAG-l-/- mice. This indicated that it is not dependent upon the presence of mature lymphoid cells, nor necessarily related to V(D)J rearrangement events. Semi-quantitative polymerase chain reaction (PCR) and hybridization with oligonucleotides specific for V8.1, 8.2 and 8.3 showed that the V8.2 gene produced at least 90% of all the germline V8 transcripts in all of the tissues examined. The significance of these results in lymphoid cell development and for models of the regulation of V(D)J rearrangement are discussed.