Identification of thyroid hormone receptors α and β genes and their expression profiles during metamorphosis in Rana chensinensis

Abstract

To explore the role of thyroid hormones in organ remodeling during the metamorphosis of amphibians, the cDNAs of two thyroid hormone receptors (TRα and TRβ) in Rana chensinensis were identified. The 1257 bp of rcTRα cDNA encoding 418 amino acids and the 1122 bp of rcTRβ cDNA encoding 373 amino acids were cloned. Their polypeptide sequences contain two highly conserved cysteine-rich zinc fingers in the DNA-binding domain, while rcTRβ is 42 amino acids shorter in its A/B domain when compared with rcTRα. Fifty-five amino acids differed between the TRα and TRβ domains. The rcTRα and rcTRβ mRNA levels in the liver, brain, skin, and tail of tadpoles were analyzed via qRT-PCR during metamorphosis. The results showed that the changes of rcTRα mRNA levels were moderate while those of rcTRβ were dramatic in all 4 tissues during metamorphosis. In addition, the levels of rcTRβ mRNA were relatively low at premetamorphosis and reached a peak around the climax. Tissue-specific expression of rcTRα and rcTRß suggests that thyroid hormones play various roles in different organs or tissues at different developmental stages of metamorphosis.