Fish gonadotropin and thyrotropin receptors: the evolution of glycoproteinhormone receptors in vertebrates

We have cloned and characterized, for the first time in fish, two different gonadotropin receptors (GTHR) and a single thyrotropin receptor (TSHR) fro m amago salmon (Oncorhynchus rhodurus) and Nile tilapia (Oreochromis niloti cus). Phylogenetic analyses and intron/exon structure suggest that the two GTHRs in fish are comparable to tetrapod follicle stimulating hormone and l uteinizing hormone receptors. Temporal and spatial expression patterns, exa mined by Northern blot analysis and in situ hybridization, paralleled those seen in mammals and birds. Consequently, genetic and functional divergence of two GTHRs and TSHR probably occurred before the teleost and tetrapod sp lit. (C) 2001 Elsevier Science Inc. All rights reserved.