RESEARCH ARTICLE Demonstration of the Coexistence of Duplicated LH Receptors in Teleosts, and Their Origin in Ancestral Actinopterygians

Pituitary gonadotropins, FSH and LH, control gonad activity in vertebrates, via binding to their respective receptors, FSHR and LHR, members of GPCR superfamily. Until recently, it was accepted that gnathostomes possess a single FSHR and a single LHR, encoded by fshr and lhcgr genes. We reinvestigated this question, focusing on vertebrate species of key-phylogenetical positions. Genome analyses supported the presence of a single fshr and a single lhcgr in chondrichthyans, and in sarcopterygians including mammals, birds, amphibians and coelacanth. In contrast, we identified a single fshr but two lhgcr in basal tel-eosts, the eels. We further showed the coexistence of duplicated lhgcr in other actinoptery-gians, including a non-teleost, the gar, and other teleosts, e.g. Mexican tetra, platyfish, or tilapia. Phylogeny and synteny analyses supported the existence in actinopterygians of two lhgcr paralogs (lhgcr1 / lhgcr2), which do not result from the teleost-specific whole-genome duplication (3R), but likely from a local gene duplication that occurred early in the actinopter-ygian lineage. Due to gene losses, there was no impact of 3R on the number of gonadotro-pin receptors in extant teleosts. Additional gene losses during teleost radiation, led to