Transcription of thyroid autoantigens in non-expressing tissues

Reverse transcriptase- polymerase chain reaction (RT-PCR) enhances the probability of detecting rare transcripts in complex mixtures of mRNA. Using thyroid autoantigens and the controversy about the role of the TSH-receptor (TSH-R) in thyroid-associated ophthalmopathy as an example, this study demonstrates the problems of interpreting RT-PCR results in typically non-expressing tissues resulting from the extremely high sensitivity of the method. Unexpected transcripts for thyroperoxidase, thyroglobulin, TSH-R (exon 1-4, 354 bp), FSH-receptor, or insulin fragments were demonstrated in a number of thyroid or orbit-derived as well as unrelated tissues or cell types. Unexpected transcripts were most prevalent in fibroblasts, irrespective of the tissue of origin and most likely caused by ectopic transcription. To establish a physiological significance of rare transcripts such as the TSH-R in orbital tissues, demonstration of the protein in addition to the positive RT-PCR results is needed.