Tissue distribution and quantitation of a gene expressing a 64-kDa antigen associated with thyroid-associated...

We have developed a competitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the quantitation of 1D mRNA, which encodes a 64-kDa protein associated with thyroid-associated ophthalmopathy, in preparations of total RNA from a variety of human tissues. This competitive RT-PCR assay is based on coamplification of competing 1D cDNA internal control template (pGEM-1D') and target cDNA template. 1D-specific mRNA was quantified in 10 human tissues. The level of 1D transcript expression in these tissues decreased in the following order: thyroid (5 pg/mg total RNA) > eye muscle (3.2 pg/mg) > skeletal muscle (2.4 pg/mg) > ovary (2 pg/mg) > cerebellum (0.4 pg/mg), kidney (0.33 pg/mg), pancreas (0.27 pg/mg), spleen (0.22 pg/mg), and thymus (0.19 pg/microgram) > retina (0.016 pg/mg). Graves' disease may be a multisystem autoimmune disorder of the connective tissue and skeletal muscle (and thyroid) that is mainly localized in the orbit and skin. One mechanism for this localization may be increased expression of target autoantigens, of which the 64-kDa protein 1D is a candidate, in the involved tissues. The higher expression of the 1D molecule in thyroid and eye supports this hypothesis.