cDNA cloning of thyroid hormone receptor betas from the conger eel, Conger myriaster

Two distinct TRbetas cDNA clones were generated by RACE from a conger eel (Conger myriaster). The deduced amino acid sequences of the conger eel TRbetas (cTRbetas) showed higher homologies to the known TRbetas of other vertebrate animals than to TRalphas. Two cTRbetas possessed an insertion sequence in the hinge region similar to other teleost fish TRbetas. Variation in cTRbeta due to differential splicing in the hinge region of the cTRbetas genes was found using PCR analysis. The determination of TRbeta mRNA levels in eel tissue was performed using competitive RT-PCR. The cTRbeta1 mRNA was widely expressed, whereas cTRbeta 2 mRNA was most highly expressed in the brain and pituitary. The expression pattern of cTRbeta1 and cTRbeta2 in tissues were similar to that of TRbeta1 and TRbeta2 in mammals.