A novel form of gonadotropin-releasing hormone in the medaka, Oryzias latipes

The present study has identified three molecular forms of gonadotropin-rele asing hormone (GnRH) in the brain of a teleost, the medaka, by isolation of their cDNAs, This species has a novel GnRH, which is here named medaka-typ e GnRH (mdGnRH), in addition to two characterized forms, chicken-II-type Gn RH (cGnRH-II) and salmon-type GnRH (sGnRH), Phylogenetic analysis showed th at mdGnRH is a medaka homolog of and seabream-type GnRH (sbGnRH) and mammal ian-type GnRH (mGnRH) in other species, and suggested that all vertebrates have three distinct GnRHs, Furthermore, in situ hybridization revealed that the mdGnRH gene is expressed only in neurons clustered within the preoptic area as sbGnRH and mGnRH genes in other species are, while the genes for c GnRH-II and sGnRH are only in the midbrain tegmentum and nucleus olfactoret inalis, respectively. This result suggested that mdGnRH is a hypophysiotrop ic factor and the other two forms are involved in other physiological event s as neuromodulators or neurotransmitters. (C) 2000 Academic Press.