title: Discovery of a gonad-specific IGF subtype in teleost.
abstract: Distinct from the conventional IGFs (IGF-1 and IGF-2), here we report the identification of a novel IGF (herein called IGF-3) encoded by a separate gene from teleost species. The IGF-3 cDNA sequences were cloned from tilapia and zebrafish, and predicted from the medaka genome and EST databases. Similar to IGF-1 and IGF-2, IGF-3 is also comprised of five domains (B, C, A, D, E) with a similar tertiary protein structure, despite a low sequence homology among them. Phylogenetic analysis reveals that the IGF-3 sequences from different teleosts cluster to form a distinctive clade separate from IGF-1 and IGF-2. The expression of this novel IGF-3 is gonad-specific and starts early in fish development. In situ hybridization revealed that IGF-3 is expressed in the somatic cells and later in granulosa cells of the ovary, and in the interstitial cells of the testis. These findings highlight the importance of this novel IGF in teleost gonadal development and reproduction.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Science, Southwest University, Chongqing 400715, China.
authors.forename: De-Shou
authors.initials: DS
authors.lastname: Wang
authors.forename: Baowei
authors.initials: B
authors.lastname: Jiao
authors.forename: Chongjiang
authors.initials: C
authors.lastname: Hu
authors.forename: Xigui
authors.initials: X
authors.lastname: Huang
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Liu
authors.forename: Christopher H K
authors.initials: CH
authors.lastname: Cheng
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006066:Gonads / Q000378:metabolism*; D008969:Molecular Sequence Data; D046468:Sexual Development / Q000502:physiology*; D013002:Somatomedins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D017210:Tilapia / Q000378:metabolism*; D014018:Tissue Distribution; D015027:Zebrafish / Q000378:metabolism*
chemical_list: D013002:Somatomedins