Isolation and Characterization of Thyroid Hormone Receptors (TRα and TRβ) in Black Rock Fish, Sebastes schlegelii

Thyroid hormones triiodothyronine (T3) and thyroxine (T4) play a vital role for developmental and physiological functions in vertebrates. They are mediated via thyroid hormone receptors (TR). In the present paper we describe the cloning and characterization of two TR genes, thyroid hormone receptor alpha (TRα) and thyroid hormone receptor beta (TRβ) from ovary mRNA of a ovoviviparous fish Sebastes schlegelii. Results revealed that main domains and motifs of the two genes were highly conserved. Quantitative real time PCR showed that the mRNA expression levels of both TRα and TRβwere high at 5 dps and slightly lower and constant during 10, 20 and 33 dps. In 105 days old juveniles and three years mature fish, the expression level was higher in gonads, brain, liver and kidney than in other tissues. The highest expression was observed in the gonads. The developmental and tissue expression patterns indicated their involvement in the growth and gonadal development. TRα exhibited higher expression than TRβ at all developmental stages and in all detected tissues except female liver, which might indicate the functional differences of these two genes.