title: Three mRNA species for mammalian-type gonadotropin-releasing hormone in the brain of the eel Anguilla japonica.
abstract: A variant mRNA species for mammalian-type gonadotropin-releasing hormone (mGnRH) that retains first intron has recently been found in the brain of a primitive teleost, the eel Anguilla japonica. Here we have found that this mRNA species is generated from an alternative upstream transcription start site of the mGnRH gene. In addition, the upstream start site produces another mRNA species that lacks first intron. Both of these two variant mRNA species, however, have the same open reading frame as the downstream mGnRH mRNA, whose introns are all spliced out, and therefore, all three mGnRH mRNA species expressed in the eel brain would translate a common prepro-mGnRH polypeptide. Quantitative analysis revealed that the upstream mRNAs are less abundant accounting for not more than 1% of the total mGnRH mRNAs. When testosterone was administered (1 mg per fish per day) continuously for 5 days to juvenile male eels, both upstream and downstream mGnRH mRNA species in the brain were up-regulated. However, the level of the upstream mRNAs increased by 3-5-fold after 12 days of the treatment, whereas that of the downstream mRNA showed a more modest increase (about 2-fold) although this increase was more rapid. These results demonstrate that both upstream and downstream mGnRH mRNAs in the eel brain are under the hormonal control, but they are regulated in different and independent manners.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, 113-8657, Tokyo, Japan.
authors.forename: Kataaki
authors.initials: K
authors.lastname: Okubo
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suetake
authors.forename: Katsumi
authors.initials: K
authors.lastname: Aida
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D016384:Consensus Sequence; D004524:Eels / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005796:Genes; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008322:Mammals / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification*; D013045:Species Specificity; D016385:TATA Box; D013739:Testosterone / Q000494:pharmacology; D024363:Transcription Initiation Site
chemical_list: D020121:5' Untranslated Regions; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone