title: Characterization and expression of cDNAs encoding P450c17-II (cyp17a2) in Japanese eel during induced ovarian development.
abstract: Estradiol-17β (E2) and maturation-inducing hormone (MIH) are two steroid hormones produced in the teleost ovary that are required for vitellogenic growth and final oocyte maturation and ovulation. During this transition, the main steroid hormone produced in the ovary shifts from estrogens to progestogens. In the commercially important Japanese eel (Anguilla japonica), the MIH 17α,20β-dihydroxy-4-pregnen-3-one (DHP) is generated from its precursor by P450c17, which has both 17α-hydroxylase and C17-20 lyase activities. In order to elucidate the regulatory mechanism underlying the steroidogenic shift from E2 to DHP and the mechanistic basis for the failure of this shift in artificially matured eels, the cDNA for cyp17a2-which encodes P450c17-II-was isolated from the ovary of wild, mature Japanese eel and characterized, and the expression patterns of cyp17a1 and cyp17a2 during induced ovarian development were investigated in cultured eel ovaries. Five cDNAs (types I-V) encoding P450c17-II were identified that had minor sequence variations. HEK293T cells transfected with all but type II P450c17-II converted exogenous progesterone to 17α-hydroxyprogesterone (17α-P), providing evidence for 17α-hydroxylase activity; however, a failure to convert 17α-P to androstenedione indicated that C17-20 lyase activity was absent. Cyp17a2 mRNA was expressed mainly in the head kidney, ovary, and testis, and quantitative PCR analysis demonstrated that expression in the ovary increased during induced vitellogenesis and oocyte maturation/ovulation. In contrast, P450c17-I showed both 17α-hydroxylase and C17-20 lyase activities, and cyp17a1 expression increased until the mid-vitellogenic stage and remained high thereafter. Considering the high level of cyp17a2 transcript in the eel ovary at the migratory nucleus stage together with our previous report demonstrating that eel ovaries have strong 17α-P-to-DHP conversion activity, the failure of artificially maturing eels to produce the maturation-inducing DHP may be explained by a deficiency in 17α-P production due to the persistence of cyp17a1 expression after the completion of vitellogenesis.
authors.affiliation: Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakkodate, Hokkaido 041-8611, Japan; College of Fisheries and Life Science, Shanghai Ocean University, Hucheng Huan Road 999, Shanghai 201306, PR China. Electronic address: su@genzentrum.lmu.de.
authors.forename: Ting
authors.initials: T
authors.lastname: Su
authors.affiliation: Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakkodate, Hokkaido 041-8611, Japan. Electronic address: ijiri@fish.hokudai.ac.jp.
authors.forename: Shigeho
authors.initials: S
authors.lastname: Ijiri
authors.affiliation: Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakkodate, Hokkaido 041-8611, Japan. Electronic address: kanbara912@ec.hokudai.ac.jp.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kanbara
authors.affiliation: Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakkodate, Hokkaido 041-8611, Japan. Electronic address: shagihara@fish.hokudai.ac.jp.
authors.forename: Seishi
authors.initials: S
authors.lastname: Hagihara
authors.affiliation: School of Life Science, Southwest University, Tiansheng Road No. 1, Beibei, Chongqing 400715, PR China. Electronic address: wdeshou@swu.edu.cn.
authors.forename: De-Shou
authors.initials: DS
authors.lastname: Wang
authors.affiliation: Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakkodate, Hokkaido 041-8611, Japan. Electronic address: s-adachi@fish.hokudai.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Adachi
mesh_terms: D000595:Amino Acid Sequence; D000811:Anguilla / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics*; D004958:Estradiol / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010053:Ovary / Q000196:embryology*; D011374:Progesterone / Q000378:metabolism; D011372:Progestins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012737:Sex Factors; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D013256:Steroids / Q000378:metabolism; D013737:Testis / Q000378:metabolism; D014818:Vitellogenesis / Q000502:physiology*
chemical_list: D018076:DNA, Complementary; D011372:Progestins; D012333:RNA, Messenger; D013256:Steroids; D011374:Progesterone; D004958:Estradiol; D013254:Steroid 17-alpha-Hydroxylase
keywords: Artificial maturation; Japanese eel; Ovary; P450c17-II; Steroidogenesis; cyp17a2