Nonfunctional thyroglobulin messenger RNA in goats with hereditary congenital goiter.

A goat strain with congenital goiter was studied as a model for human thyroid disoders. These goats were deficient in thyroglobulin (Tg), the precursor protein of the thyroid hormones T3 and T4. RNA coding for Tg (Tg-RNA) was detected in reduced amounts in the goiters and was almost absent from the membranes, where Tg is normally synthesized. This paper describes the preparation and characterization of a goat Tg cDNA plasmid and its use in the study of thyroglobulin gene expression in the goiter. We found that the goiter Tg-RNA is polyadenylated and has the same size as normal 33S goat TG mRNA. Thus, there are no major defects in the mRNA processing. However, in contrast to normal Tg mRNA, the goiter Tg-RNA was not translated into immunoprecipitable Tg subunits when injected into Xenopus oocytes. We conclude therefore that the goiter Tg-RNA has one or more alterations causing a lack of proper translation and/or a decreased cytoplasmic stability.