title: Molecular and evolutionary characterization of the GnRH-II gene in the chicken: distinctive genomic organization, expression pattern, and precursor sequence.
abstract: Of all the structural variants of GnRH (gonadotropin-releasing hormone), GnRH-II has been found to be universally present in and uniquely conserved among jawed vertebrates without any sequence substitutions. Our previous study found that the GnRH-II precursor sequences have become divergent in the lineage of eutherian mammals, based on a comparison between reptilian and mammalian GnRH-II. To elucidate the molecular evolution of GnRH-II throughout amniotes, we have performed the first identification of the avian GnRH-II cDNA/gene from the chicken, the species used for the initial discovery of GnRH-II peptide. Gene arrangement around the GnRH-II in the chicken was similar to that in mammals; however, a gene MRPS26 was partly overlapped with the downstream part of the GnRH-II in the chicken. It was identified that the GnRH-II/MRPS26 locus generated at least five distinct types of transcripts with different expression patterns and three of them may produce functional GnRH-II decapeptide. Sequence comparison revealed that the prepro-GnRH-II polypeptide of the chicken was substantially different from those of other species regarding the length and similarity. The present results strongly indicated that considerable variations were generated in the precursor sequence of the evolutionarily conserved GnRH-II during amniote evolution. It was also suggested that the sequence divergence seen in the chicken may have occurred independently of that in the mammalian lineage.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. tikemoto@infoseek.jp
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Ikemoto
authors.forename: Min Kyun
authors.initials: MK
authors.lastname: Park
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D002645:Chickens / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D023061:Gene Order; D014644:Genetic Variation; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D007438:Introns / Q000235:genetics*; D008845:Microinjections; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D011498:Protein Precursors / Q000235:genetics*; D020537:RNA, Small Nucleolar / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D020121:5' Untranslated Regions; D011498:Protein Precursors; D020537:RNA, Small Nucleolar; D007987:Gonadotropin-Releasing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-