title: Identification and gene expression analyses of ghrelin in the stomach of Pacific bluefin tuna (Thunnus orientalis).
abstract: Full length cDNA and gene encoding ghrelin precursor and mature ghrelin peptide were identified from the stomach of Pacific bluefin tuna, Thunnus orientalis, which has unique metabolic physiology and high commercial value at fishery markets. Quantitative expression analysis was conducted for the gastric ghrelin and pepsinogen 2 genes during the early stage of somatic growth from the underyearling to yearling fish. The full length cDNA of bluefin tuna ghrelin precursor has a length of 470bp and the deduced precursor is composed of 107 amino acids. The ghrelin gene is 1.9kbp in length and has a 4 exon-3 intron structure. The major form of mature ghrelin in the stomach was an octanoylated 20-amino acid peptide with C-terminal amidation, while overall 12 different forms of ghrelin peptides, including short form of 18-amino acid peptide and seven kinds of acyl modifications were identified. The expression profiles of the gastric ghrelin and pepsinogen 2 genes showed no significant changes related to the early growth stages. The present results suggest that digestive physiology has already been functional in this growth stage of the juvenile bluefin tuna and ghrelin may have a role in the sustained digestive and metabolic activities.
authors.affiliation: Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaiya
authors.forename: Hideki
authors.initials: H
authors.lastname: Nikaido
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shiozawa
authors.forename: Kenzo
authors.initials: K
authors.lastname: Mishiro
authors.forename: Hironori
authors.initials: H
authors.lastname: Ando
mesh_terms: D000818:Animals; D018076:DNA, Complementary; D054439:Ghrelin / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D014413:Tuna / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D054439:Ghrelin