title: IGFs mediate the action of LH on oocyte maturation in zebrafish.
abstract: LH signaling is required for oocyte maturation in fish and other vertebrates. However, the downstream factors mediating LH signaling are largely unexplored in fish. In this study, we investigated whether IGFs could mediate LH action on oocyte maturation in zebrafish. Our results show that all igfs, including igf1, igf2a, igf2b, and igf3, are dynamically expressed during folliculogenesis, with the expression of igf3 reaching its maximal level in full grown stage follicles. The expression of igfs is regulated by LH through a cAMP pathway in intact follicles as well as in primary cultured follicular cells, with igf3 expression being the most sensitive to human chorionic gonadotropin (hCG) treatment. Moreover, recombinant zebrafish IGF-2a, IGF-2b, and IGF-3 proteins significantly enhanced oocyte maturation via IGF-1 receptors (IGF-1rs), with IGF-3 exhibiting the most potent stimulatory action on oocyte maturation. Furthermore, we have demonstrated that IGF-3 or hCG treatment could stimulate IGF-1rs phosphorylation, and hCG-induced oocyte maturation could be attenuated by IGF-1r inhibitors as well as by an anti-IGF-3 antiserum in vitro and in vivo, indicating that the IGF system especially IGF-3 plays a crucial role in mediating LH action on oocyte maturation. In addition, igf3 expression is significantly attenuated in LH β-subunit (lhb) mutant zebrafish and treatment with recombinant IGF-3 could partially rescue the oocyte maturation defects of the lhb mutants in vitro and in vivo. Collectively, our results clearly demonstrated that IGFs, particularly the gonad-specific IGF-3, act as important mediators of LH action on oocyte maturation in zebrafish.
authors.affiliation: College of Life Sciences (J.L.), Northwest Normal University, Lanzhou, 730070 China; and School of Biomedical Sciences (J.L., L.C., X.S., Y.L., C.H.K.C.), The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Jianzhen
authors.initials: J
authors.lastname: Li
authors.forename: Lianhe
authors.initials: L
authors.lastname: Chu
authors.forename: Xiao
authors.initials: X
authors.lastname: Sun
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Christopher H K
authors.initials: CH
authors.lastname: Cheng
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D055786:Gene Knockout Techniques; D006801:Humans; D007106:Immune Sera; D007334:Insulin-Like Growth Factor I; D037101:Luteinizing Hormone, beta Subunit / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D038081:Organogenesis / Q000187:drug effects / Q000235:genetics; D006080:Ovarian Follicle / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013002:Somatomedins / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*
chemical_list: D006063:Chorionic Gonadotropin; D007106:Immune Sera; D037101:Luteinizing Hormone, beta Subunit; D011994:Recombinant Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1