Phylogenetic analysis of the vertebrate glycoprotein hormone family including new sequences of sturgeon (Acipenser baeri) beta subunits of the two gonadotropins and the thyroid-stimulating hormone

The beta subunits of the two gonadotropins (GTH1 and GTH2) and of the thyro id-stimulating hormone (TSH) of a chondrostean fish, Acipenser baeri, were cloned. These new sequences and selected representative members of beta sub units of vertebrate glycoprotein hormones, including tetrapod follicle-stim ulating hormones (FSH) and luteinizing hormones (LH), allowed us to infer t he phylogenetic relationships within this family. Both distance matrix and maximum parsimony methods were used on both nucleotide and amino acid seque nces, with bootstrapping evaluation over 1000 replicates. The four trees ob tained had highly similar topologies. In each case, three monophylogenetic lineages, TSH, GTH1-FSH, and GTH2-LH were clearly identified, The three mon ophylogenetic lineages were supported by 21-23 specific characters at the a mino acid level, out of a total of 121 characters. The resolved topologies within each monophyletic hormone cluster were congruent with the known phyl ogenetic relationships between the related species. The inferred parental r elationships within gonadotropins are in agreement with data concerning the ir biological functions. The present study demonstrates that GTH1 and GTH2 are the actinopterygian homologues of tetrapod FSH and LH, respectively.