title: Identification of the growth hormone receptor in an advanced teleost, the tilapia (Oreochromis mossambicus) with special reference to its distinct expression pattern in the ovary.
abstract: There is considerable evidence that the GH/IGF-I axis plays an important role in female reproduction. We report the isolation and characterization of the GH receptor (GH-R) and its gene expression profile during oogenesis in the tilapia, Oreochromis mossambicus. cDNA encoding GH-R was cloned and sequenced from the tilapia liver. The predicted GH-R preprotein consisted of 635 amino acids and contained a putative signal peptide, an extracellular region with a characteristic motif, a single transmembrane region, and a cytoplasmic region with conserved box 1 and 2 domains. The tilapia GH-R shared 34-74% identities with known GH-Rs in vertebrates. A binding assay using COS-7 cells showed that the cloned GH-R bound specifically to tilapia GH. Northern blot analysis showed a single mRNA transcript in the liver and ovary. In situ hybridization revealed intense signals of GH-R in the cytoplasm and nucleus of immature oocytes. The granulosa and theca cells surrounding vitellogenic oocytes also contained the GH-R mRNA signals. About a tenfold greater level of GH-R mRNA was found in the immature oocytes versus the mature oocytes, along with high levels of IGF-I mRNA. There were no significant changes in mRNA levels of GH-R and IGF-I in the liver or in plasma IGF-I levels during oocyte development. No correlation was found between hepatic GH-R mRNA and ovarian GH-R mRNA. These results suggest that the GH/IGF-I axis in the ovary may be involved in the early phases of oogenesis, under a different regulatory mechanism of GH-R gene expression from that of the liver.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kajimura
authors.forename: N
authors.initials: N
authors.lastname: Kawaguchi
authors.forename: T
authors.initials: T
authors.lastname: Kaneko
authors.forename: I
authors.initials: I
authors.lastname: Kawazoe
authors.forename: T
authors.initials: T
authors.lastname: Hirano
authors.forename: N
authors.initials: N
authors.lastname: Visitacion
authors.forename: E G
authors.initials: EG
authors.lastname: Grau
authors.forename: K
authors.initials: K
authors.lastname: Aida
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D019556:COS Cells; D002467:Cell Nucleus / Q000737:chemistry; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003593:Cytoplasm / Q000737:chemistry; D005260:Female; D005399:Fishes; D015870:Gene Expression; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D008099:Liver / Q000737:chemistry; D008969:Molecular Sequence Data; D009865:Oocytes / Q000737:chemistry; D009866:Oogenesis; D010053:Ovary / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis*; D011869:Radioligand Assay; D051381:Rats; D011986:Receptors, Somatotropin / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017210:Tilapia / Q000378:metabolism*; D014162:Transfection
chemical_list: D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I