Piscine (Sparus aurata) transthyretin cDNA cloning and characterization

Transthyretin (TTR) is one of the three plasma proteins that participate in the transport of thyroid hormones, thyroxine (T4) and triiodothyronine (T3); it is also involved in the carriage of retinol through the mediation of retinol-binding protein.1 The liver and choroid plexus are the major sites of TTR synthesis in mammals, birds, and diprotodont marsupials; in reptiles, TTR is only synthesized in the choroid plexus. 2 cDNA coding for TTR has been cloned from several mammalian, reptilian, and avian species and is highly conserved especially in the domains involved in binding to thyroid hormones.3 TTR expression has never been reported in fish, in which albumin is considered to be the main carrier for T3 and T4.2 We report the cloning of a TTR cDNA from sea bream (Sparus aurata) and demonstrate the presence of TTR mRNA in the liver of this fish