Germline transcription of multiple TCR-V beta genes in cloned T-cell lines

The functional significance of germline transcription of T cell receptor (TCR) beta chain variable (V) region genes is under investigation. The accepted model is that transcriptional activation of germline TCR genes is associated with the rearrangement process during T-cell development. By this model, germline expression of a subset of TCR-Vbeta genes might be expected in early T cells which have not yet undergone rearrangement. Germline transcription of TCR-Vbeta genes was analysed using the reverse transcriptase (RT)-PCR in a clonal T-cell precursor line C1-V13D, a clonal pre-B cell line RAW 112 and a mature T helper cell line D10.G4.1. Evidence is presented for germline transcription of TCR-VP8.2 and TCR-Vbeta2.1 genes in all three cell lines, although expression in RAW112 was very weak. C1-V13D cells expressed very high levels of the whole range of transcripts including Vbeta2.1, Vbeta5.1, Vbeta5.2, Vbeta6.1, Vbeta7.1, Vbeta8.1, Vbeta8.2, Vbeta8.3 and Vbeta13.1. However, D10.G4.1 cells expressed a subset of transcripts with apparently lower levels of expression, including Vbeta2.1, Vbeta5.1, Vbeta5.2, Vbeta6.1, Vbeta8.2 and Vbeta8.3. These results raise questions about the significance and possible function of germline transcripts and/or their encoded products in early lymphoid cells and in T cells at different stages of development.