title: Molecular cloning of zebrafish and medaka vitellogenin genes and comparison of their expression in response to 17beta-estradiol.
abstract: In the present study, both zebrafish and medaka vitellogenin genes have been isolated and used as a biomarker to compare the two small aquarium fish in response to estrogen treatment and thus to evaluate the two fish models in development of a biomonitoring system for environmental estrogens. The isolated zebrafish vitellogenin gene, zvtg1, is the most abundantly expressed vitellogenin gene in zebrafish and its complete protein sequence of 1360 amino acids was deduced from a genomic and a cDNA clone. The isolated medaka vitellogenin (mvtg1) genomic clone covers 1053 amino acids in the N-terminal. Both zebrafish zvtg1 and medaka mvtg1 are specifically expressed in female liver and their expression can be induced by 17beta-estradiol (E2) in male fish both by intramuscular injection and immersion treatment. A real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay was developed for quantification of vitellogenin mRNA level in both control fish and E2-treated fish. The lowest-observed-effect concentrations of E2 for the induction of vitellogenin mRNAs were observed at 1 microg/l for zebrafish and 0.1 microg/l for medaka in a 2-day exposure experiment. Further kinetics studies of the two fish models indicated that medaka was able to respond much faster to E2 treatment than zebrafish, while the zebrafish can attain a much higher level of vitellogenin mRNAs than medaka after a long-term E2 treatment. The implication of these observations may be that the medaka system is better in monitoring acute treatment while the zebrafish system is better in monitoring chronic exposure.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Block S2 No. 05-17, 14 Science Drive 4, 10 King Ridge Crescent, Singapore 119260, Singapore.
authors.forename: Yan
authors.initials: Y
authors.lastname: Tong
authors.forename: Tao
authors.initials: T
authors.lastname: Shan
authors.forename: Yew Kwang
authors.initials: YK
authors.lastname: Poh
authors.forename: Tie
authors.initials: T
authors.lastname: Yan
authors.forename: Hai
authors.initials: H
authors.lastname: Wang
authors.forename: Siew Hong
authors.initials: SH
authors.lastname: Lam
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Gong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004958:Estradiol / Q000494:pharmacology*; D005091:Exons; D005260:Female; D015870:Gene Expression / Q000187:drug effects* / Q000235:genetics; D005796:Genes / Q000235:genetics; D007438:Introns; D008297:Male; D008969:Molecular Sequence Data; D009990:Oryzias / Q000235:genetics*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D014819:Vitellogenins / Q000235:genetics*; D015027:Zebrafish / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D014819:Vitellogenins; D029961:Zebrafish Proteins; C486450:vtg1 protein, zebrafish; D004958:Estradiol; D004247:DNA