title: Identification and characterization of a catechol-o-methyltransferase cDNA in the catfish Heteropneustes fossilis: Tissue, sex and seasonal variations, and effects of gonadotropin and 2-hydroxyestradiol-17β on mRNA expression.
abstract: Catechol-O-methyltransferase (COMT) is involved in the methylation and inactivation of endogenous and xenobiotic catechol compounds, and serves as a common biochemical link in the catecholamine and catecholestrogen metabolism. Studies on cloning, sequencing and function characterization comt gene in lower vertebrates like fish are fewer. In the present study, a full-length comt cDNA of 1442bp with an open-reading frame (ORF) of 792bp, and start codon (ATG) at nucleotide 162 and stop codon (TAG) at nucleotide 953 was isolated and characterized in the stinging catfish Heteropneustes fossilis (accession No. KT597925). The ORF codes for a protein of 263 amino acid residues, which is also validated by the catfish transcriptome data analysis. The catfish Comt shared conserved putative structural regions important for S-adenosyl methionine (AdoMet)- and catechol-binding, transmembrane regions, two glycosylation sites (N-65 and N-91) at the N-terminus and two phosphorylation sites (Ser-235 and Thr-240) at the C-terminus. The gene was expressed in all tissues examined and the expression showed significant sex dimorphic distribution with high levels in females. The transcript was abundant in the liver, brain and gonads and low in muscles. The transcripts showed significant seasonal variations in the brain and ovary, increased progressively to the peak levels in spawning phase and then declined. The brain and ovarian comt mRNA levels showed periovulatory changes after in vivo and in vitro human chorionic gonadotropin (hCG) treatments with high fold increases at 16 and 24h in the brain and at 16h in the ovary. The catecholestrogen 2-hydroxyE2up regulated ovarian comt expression in vitro with the highest fold increase at 16h. The mRNA and protein was localized in the follicular layer of the vitellogenic follicles and in the cytoplasm of primary follicles. The data were discussed in relation to catecholamine and catecholestrogen-mediated functions in the brain and ovary of the stinging catfish.
authors.affiliation: Department of Zoology, Banaras Hindu University, Varanasi 221005, India.
authors.forename: R
authors.initials: R
authors.lastname: Chaube
authors.affiliation: Department of Zoology, Banaras Hindu University, Varanasi 221005, India.
authors.forename: A
authors.initials: A
authors.lastname: Rawat
authors.affiliation: Department of Zoology, Madras Christian College, Chennai 600059, India.
authors.forename: R M
authors.initials: RM
authors.lastname: Inbaraj
authors.affiliation: INRA LPGP UR037, Fish Physiology and Genomics, Campus de Beaulieu, F-35042 Rennes Cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Bobe
authors.affiliation: INRA LPGP UR037, Fish Physiology and Genomics, Campus de Beaulieu, F-35042 Rennes Cedex, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Guiguen
authors.affiliation: INRA LPGP UR037, Fish Physiology and Genomics, Campus de Beaulieu, F-35042 Rennes Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Fostier
authors.affiliation: Department of Biotechnology, Cochin University of Science and Technology, Kochi 682022, India. Electronic address: kpjoybhu@gmail.com.
authors.forename: K P
authors.initials: KP
authors.lastname: Joy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D002394:Catechol O-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D002397:Catfishes / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006062:Gonadotropins / Q000494:pharmacology*; D006066:Gonads / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D010053:Ovary / Q000187:drug effects / Q000201:enzymology*; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D012621:Seasons; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: D006063:Chorionic Gonadotropin; D018076:DNA, Complementary; D006062:Gonadotropins; D012333:RNA, Messenger; D004958:Estradiol; C001390:2-hydroxyestradiol; D002394:Catechol O-Methyltransferase
keywords: Catecholestrogen; De novo assembled catfish transcriptome; Hormonal control of comt cDNA; Molecular cloning of comt; Phylogeny; Sex and seasonal variations