Identification of two isoforms of Atlantic halibut insulin-like growth factor-I receptor genes and quantitative gene expression during metamorphosis.
Insulin-like growth factor-I (IGF-I) is an important regulator of growth and development in vertebrates. Both the endocrine and paracrine actions of IGF-I are mediated through ligand-binding to a membrane-bound IGF-I receptor (IGF-IR). The characterization of this receptor and subsequent expression studies thus help elucidate the endocrine regulation of developmental processes. As other flatfish species, the Atlantic halibut (Hippoglossus hippoglossus) undergoes a dramatic larval metamorphosis. This process is largely under endocrine control, and data indicate that IGF-I could be a key regulator. IGF-I content increases up to late pre-metamorphosis and decreases during metamorphosis. The IGF-IR has, however, not been studied during flatfish metamorphosis. To examine IGF-IR gene expression, two IGF-IR mRNA were cloned and sequenced. These partial sequences share high identity (>or=95%) and similarity (>or=97%) with other fish IGF-IR and lower identity (>or=77%) and similarity (>or=83.5%) with Japanese flounder insulin receptors. The expression of mRNA for both IGF-IR was analyzed by quantitative real-time RT-PCR during six larval developmental stages from pre- to post-metamorphosis. IGF-IR1 and IGF-IR2 mRNA are differentially expressed during metamorphosis, but if this indicates an isoform-specific regulation of developmental processes by circulating and/or locally-secreted IGF-I is unclear. Both IGF-IR genes are down-regulated in halibut larvae experiencing arrested metamorphosis, suggesting the IGF-I system is critical for metamorphic success in halibut.
Hildahl
Jon
J
Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, Göteborg University, Göteborg, Sweden. jon.hildahl@zool.gu.se <jon.hildahl@zool.gu.se>
Galay-Burgos
Malyka
M
Sweeney
Glen
G
Einarsdóttir
Ingibjörg Eir
IE
Björnsson
Björn Thrandur
BT
D000818:Animals; D001483:Base Sequence; D029941:Fish Proteins / Q000096:biosynthesis* / Q000235:genetics*; D005432:Flounder / Q000196:embryology* / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis* / Q000235:genetics*
D029941:Fish Proteins; D012333:RNA, Messenger; D017526:Receptor, IGF Type 1