Characterization of a sea bream (Sparus aurata) thyroid hormone receptor-beta clone expressed during embryonic and larval development

A clone encoding thyroid hormone receptor-beta (TR-beta) was isolated from a sea bream (Sparus aurata) ovary cDNA library. Sea bream (sb)TR-beta is cl osely related to its counterparts from other vertebrates and, like them, pr eferentially binds T-3 rather than T-4. However, the putative sbTR-beta pro tein contains a nine-amino-acid insert that is also present in the correspo nding proteins from flounder and salmon but absent in TR-betas from zebrafi sh and terrestrial vertebrates. Semiquantitative RT-PCR analysis showed tha t sbTR-beta transcripts begin to accumulate during gastrulation and increas e markedly in quantity up to the period around hatch (ca. 40 h postfertiliz ation) before declining slightly. In adult tissues, TR-beta mRNA was presen t in approximately equal quantities in heart, intestine, brain, kidney, ske letal muscle, liver, and gill. The significance of the relatively strong ex pression of TR-beta during sea bream embryogenesis is discussed, (C) 2001 A cademic Press.