Isolation, characterization, cDNA cloning and gene expression of an avian transthyretin

Abstract

A chicken liver cDNA library was constructed in bacteriophage AgtlO. A full-length transthyretin cDNA clone was identified by screening with rat transthyretin cDNA and was sequenced. A three-dimensional model of chicken transthyretin was obtained by computer-graphics-based prediction from the derived amino acid sequence for chicken transthyretin and from the structure of human transthyretin determined by X-ray diffraction analysis

Evolution of Transthyretin in Marsupials

“…The entire M. dornestica transthyretin cDNA sequence displays 67-73 %, 65% and 65% identity to eutherian (Mita et al, 1984;Dickson et al, 1985b;Wakasugi et al, 1985;Fung et al, 1988;Duan et al, 1989;Tu et al, 1989), chicken and lizard (Achen et al, 1993) transthyretin cDNAs, respectively. The mass of the subunit of M. dornestica transthyretin, calculated from the deduced amino acid sequence, is 14317 Da, assuming no post-translational modifications.…”

“…L2 is a degenerate primer for the complementary strand corresponding to the DNA segment coding for residues 1 13 -108 of mammalian and chicken transthyretins. Approximately 1 pg recombinant bacteriophage DNA was amplified by the polymerase chain reaction, as described by Duan et al (1991), except that the following cycle profiles were used: denaturation at 95°C for 5 min, followed by 35 cycles of annealing at 45 "C for 40 s, extension at 68 "C for 30 s and denaturation at 95°C for 30 s.…”

“…Transthyretin is the major protein synthesised and secreted by the choroid plexus of all vertebrates, except fish and amphibians. Transthyretin gene expression occurs in the liver in birds and all eutherians (also called placental mammals), but not in fish, amphibians, reptiles and monotremes (Dickson et al, 1985a(Dickson et al, ,b, 1986Duan et al, 1991 ;Harms et al, 1991 ;Achen et al, 1992Achen et al, , 1993Aldred et al, 1992;Schreiber et al, 1993). Apparently, transthyretin gene expression in the liver evolved independently in the evolutionary lineages leading to birds and to eutherians.…”

Lutein associated with a transthyretin indicates carotenoid derivation and novel multiplicity of transthyretin ligands

“…While, the synthesis in the choroid plexus is found in species down to reptiles, that in liver is found only in mammals, one group of marsupials, and birds [6,7,9]. TTR is also produced in the c~ cells of the human Langerhan's islets, but in the ft cells or in both theft and ~ cells in other species [10].…”

“…Transthyretin has two well-established functions; one is the transport of thyroxine [4], the other the transport of retinol via the TTR-associated retinol binding protein (RBP) [5], but other functions have also been considered. The protein is structurally well conserved throughout evolution [6], particularly in its thyroxine-binding channel, but TTR is not essential for life as it is absent in amphibian and lower vertebrate branches [7], and as TTR-null-mutant mice survive, are euthyroid, and reproduce, although with reduced levels of triiodothyronine and thyroxine, as well as extremely low levels of retinol and RBP [8].…”