Structure, developmental expression, and physiological regulation of zebrafish IGF binding protein-1.
The biological activity and availability of IGFs are regulated by a group of secreted proteins that belong to the IGF-binding protein (IGFBP) gene family. Although six IGFBPs have been identified and studied in mammals, their nonmammalian orthologs remain poorly defined. In this study, we cloned and characterized the full-length zebrafish IGFBP-1. Sequence analysis indicated that its structure is homologous to mammalian IGFBP-1. Using in situ RNA hybridization and RT-PCR, we discovered that IGFBP-1 mRNA was present in all early embryonic stages albeit at very low levels. IGFBP-1 mRNA was initially expressed in multiple embryonic tissues but became restricted to the liver shortly after hatching. In the adult stage, IGFBP-1 mRNA was found only in the liver at low levels. Prolonged food deprivation caused a significant increase in the hepatic IGFBP-1 mRNA levels, and refeeding restored the IGFBP-1 mRNA to the basal levels. When adult fish or embryos were subjected to hypoxic conditions, the IGFBP-1 mRNA expression increased dramatically. Intriguingly, the hypoxia-induced IGFBP-1 expression operated in different embryonic tissues in a developmental-stage-dependent manner. In early embryos, hypoxia-stimulated IGFBP-1 mRNA expression in the pharyngeal arches, ventricle, atrium, and brain. After hatching, the hypoxia-induced IGFBP-1 expression became liver specific. These results not only provide new information about the structural conservation, developmental expression, and physiological regulation of the IGFBP-1 gene but also present the opportunity to elucidate the developmental role of IGFBP-1 using a unique vertebrate model organism.
Maures
Travis J
TJ
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor 48109, USA.
Duan
Cunming
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D016208:Databases, Factual; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism; D017403:In Situ Hybridization; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D008099:Liver / Q000196:embryology / Q000378:metabolism; D008969:Molecular Sequence Data; D009747:Nutritional Physiological Phenomena; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution; D015027:Zebrafish
D018970:Insulin-Like Growth Factor Binding Protein 1; D012333:RNA, Messenger