Gonadotropin-releasing hormone genes: Phylogeny, structure, and functions

Gonadotropin-releasing hormone (GnRH, previously called leutinizing hormone -releasing hormone, LHRH) is the final common signaling molecule used by th e brain to regulate reproduction in all vertebrates. Recently, genes encodi ng two other GnRH forms have been discovered. Here we present a phylogeneti c analysis that shows that the GnRH genes fall naturally into three distinc t branches, each of which shares not only a molecular signature but also ch aracteristic expression sites in the brain. The GnRH genes appear to have a risen through gene duplication from a single ancestral GnRH whose origin pr edates vertebrates. Several lines of data support this suggestion, includin g the fact that all three genes share an identical exonic structure. The ex istence of three distinct GnRH families suggests a new, natural nomenclatur e for the genes, and in addition, we present a logical proposal for naming the peptide sequences. The two recently discovered GnRH genes are unusual b ecause they encode decapeptides that are identical in all the species in wh ich they have been found. The control of gene expression also differs among the three gene families as might be expected since they have had separate evolutionary trajectories for perhaps 500 million years. (C) 1999 Academic Press.