Identification and characterization of two distinct GnRH receptor subtypes in a teleost, the medaka Oryzias latipes.
We report the identification and characterization of two distinct GnRH receptor (GnRH-R) subtypes, designated GnRH-R1 and GnRH-R2, in a model teleost, the medaka Oryzias latipes. These seven-transmembrane receptors of the medaka contain a cytoplasmic C-terminal tail, which has been found in all other nonmammalian GnRH-Rs cloned to date. The GnRH-R1 gene is composed of three exons separated by two introns, whereas the GnRH-R2 gene has an additional intron and therefore consists of four exons and three introns. The GnRH-R1 and GnRH-R2 genes, both of which exist as single-copy genes in the medaka genome, were mapped to linkage groups 3 and 16, respectively. Inositol phosphate assays using COS-7 cells transfected with GnRH-R1 and GnRH-R2 demonstrated that they had remarkably different ligand sensitivities, although both receptors showed highest preference for chicken-II-type GnRH. Phylogenetic analysis showed the presence of three paralogous lineages for vertebrate GnRH-Rs and indicated that neither GnRH-R1 nor GnRH-R2 is the medaka ortholog to mammalian GnRH-Rs that lack a cytoplasmic tail. This, together with an observation that medaka-type GnRH had low affinity for GnRH-R1 and GnRH-R2, suggests that a third GnRH-R may exist in the medaka.
Okubo
K
K
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Nagata
S
S
Ko
R
R
Kataoka
H
H
Yoshiura
Y
Y
Mitani
H
H
Kondo
M
M
Naruse
K
K
Shima
A
A
Aida
K
K
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000302:isolation & purification; D018628:Gene Dosage; D006801:Humans; D008969:Molecular Sequence Data; D009990:Oryzias / Q000378:metabolism*; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011966:Receptors, LHRH / Q000235:genetics / Q000378:metabolism*; D014714:Vertebrates / Q000235:genetics
D018076:DNA, Complementary; D020033:Protein Isoforms; D011966:Receptors, LHRH