Involvement of growth hormone-insulin-like growth factor I system in cranial remodeling during halibut metamorphosis as indicated by tissue- and stage-specific receptor gene expression and the presence of growth hormone receptor protein.
The role of growth hormone (GH) and insulin-like growth factor-I (IGF-I) in the tissue remodeling associated with the transition of a symmetrical larva to an asymmetrical juvenile during flatfish metamorphosis is unknown. In order to investigate the potential role of these hormones in the remodeling of cranial bone and soft tissue that accompanies eye migration during metamorphosis of Atlantic halibut (Hippoglossus hippoglossus) larvae, tissue-specific gene expression was monitored by in situ hybridization for Atlantic halibut type I growth hormone receptor (hhGHR), type II hhGHR, and insulin-like growth factor-I receptor (hhIGF-IR). Polyclonal antibody generated against the extracellular domain of type I hhGHR was used for the immunohistochemical localization of type I GHR protein. Type I hhGHR, type II hhGHR, and hhIGF-IR mRNA were expressed in fibroblasts, frontal bone osteocytes, and dorsal chondrocytes at the onset of metamorphosis (stage 8), during metamorphic climax (stage 9), and in fully metamorphosed juveniles (stage 10). Type I GHR protein showed similar expression patterns to those of type I hhGHR mRNA, except in chondrocytes in which little GHR protein was detected. The localization of GHR and IGF-IR transcripts and GHR protein in cranial structures that undergo remodeling is intriguing and suggests that, in addition to thyroid hormones, the GH-IGF-I system is involved in morphological transformations during metamorphosis in Atlantic halibut.
Hildahl
Jon
J
Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, Göteborg University, Box 436, S-40530, Göteborg, Sweden. jon.hildahl@veths.no
Power
Deborah M
DM
Björnsson
Björn Thrandur
BT
Einarsdóttir
Ingibjörg Eir
IE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019902:Chondrocytes / Q000378:metabolism; D005123:Eye / Q000254:growth & development; D005347:Fibroblasts / Q000378:metabolism; D005432:Flounder / Q000254:growth & development* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D010011:Osteocytes / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000235:genetics* / Q000378:metabolism; D011986:Receptors, Somatotropin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D012886:Skull / Q000254:growth & development* / Q000378:metabolism
D011986:Receptors, Somatotropin; D017526:Receptor, IGF Type 1