title: Characterization of the insulin-like growth factor binding protein family in Xenopus tropicalis.
abstract: The insulin-like growth factor binding protein (Igfbp) family consists of six members designated Igfbp1-6. Igfbps are involved in many vital biological functions. They physically interact with IGFs (IGF1 and IGF2) and act as carriers, thereby protecting IGFs from proteolytic degradation. Thus, they function as modulators of IGF activity. Furthermore, Igfbps have been reported to have IGF-independent activities. They interact with other proteins, including cell surface proteins, extra-cellular matrix proteins, and potentially intracellular molecules. In Xenopus tropicalis (X. tropicalis), only four igfbp genes (igfbp1, igfbp2, igfbp4, and igfbp5) have been identified, and their expression is not well characterized. We report that X. tropicalis genome lacks the igfbp3 and igfbp6 genes based on synteny analyses. We also examined the spatio-temporal expression patterns of igfbp genes in early X. tropicalis development. Expression analyses indicated that they are differentially expressed during early development. Each igfbp gene showed a characteristic spatial expression pattern. Except for igfbp5, they demonstrated overlapping expression in the pronephros. The Xenopus pronephros is composed of four domains (i.e., the proximal tubule, intermediate tubule, distal tubule, and connecting tubule). Our results showed that at least two igfbp genes are co-expressed in all pronephric domains, suggesting that redundant functions of igfbp genes are required in early pronephric kidney development.
authors.affiliation: Research Center for Stem Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Haramoto
authors.forename: Tomomi
authors.initials: T
authors.lastname: Oshima
authors.forename: Shuji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Ito
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000235:genetics; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000235:genetics; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007668:Kidney / Q000196:embryology* / Q000378:metabolism*; D015347:RNA Probes; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014981:Xenopus / Q000235:genetics* / Q000254:growth & development
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D015347:RNA Probes; D012333:RNA, Messenger