Improved peripheral T cell expression of T-cell receptor (TCR)-α transgenes in TCRα/Dad1 locus-like "two gene" reporter systems (136.14)

Abstract

The mouse T-cell receptor (TCR)-a; locus control region (LCR) resides in between the Ca; exons and the Dad1 gene. We reported the "single cell level" activity of the TCRa LCR in the context of linked heterologous single reporter transgenes randomly integrated into the genome of mice. We found that the LCR supports the normal pattern of TCRa expression in the thymus. However, abnormal ectopic expression and T cell transcript reductions were observed in the periphery. These data indicated that important cis-acting elements (not associated with the LCR) are required for strict cell type-specificity, and peripheral T cell maintenance of TCRa expression. Here we describe data from experiments with transgenic mice bearing constructs in which the LCR is flanked by two transcription units (as it is in the genome by TCRa [5'] and Dad1 [3']). In the first system, two heterologous reporter genes flank the LCR. The other system is an 80-kb TCRa/Dad1 Bacterial Artificial Chromosome (BAC) fragment in which a Va promoter driven reporter is inserted upstream of the Ca exons, followed by the TCRa LCR and the Dad1 gene locus. We find that peripheral T cells maintain expression of the TCRa reporter gene in the BAC construct. Surprisingly, in both "two-gene" reporter systems, ectopic, non-T cell expression of the TCRa reporter is virtually eliminated. The data suggest that important cis-acting elements maintaining normal TCRa expression patterns in peripheral T cells reside in the Dad 1 gene locus. Supported by NIH grants AI053050 (to BDO), RR03037 (to the Hunter College Gene Center) and UL1RR024996 (to the Clinical and Translation Science Center at Weill Cornell Medical College).