title: Leptin receptor-deficient (knockout) medaka, Oryzias latipes, show  chronical up-regulated levels of orexigenic neuropeptides, elevated  food  intake and stage specific effects on growth and fat allocation.
abstract: The first studies that identified leptin and its receptor (LepR) in mammals were based on mutant animals that displayed dramatic changes in body-weight and regulation of energy homeostasis. Subsequent studies have shown that a deficiency of leptin or LepR in homoeothermic mammals results in hyperphagia, obesity, infertility and a number of other abnormalities. The physiological roles of leptin-mediated signaling in ectothermic teleosts are still being explored. Here, we produced medaka with homozygous LepR gene mutation using the targeting induced local lesions in a genome method. This knockout mutant had a point mutation of cysteine for stop codon at the 357th amino acid just before the leptin-binding domain. The evidence for loss of function of leptin-mediated signaling in the mutant is based on a lack of response to feeding in the expression of key appetite-related neuropeptides in the diencephalon. The mutant lepr−/− medaka expressed constant up-regulated levels of mRNA for the orexigenic neuropeptide Ya and agouti-related protein and a suppressed level of anorexigenic proopiomelanocortin 1 in the diencephalon independent of feeding, which suggests that the mutant did not possess functional LepR. Phenotypes of the LepR-mutant medaka were analyzed in order to understand the effects on food intake, growth, and fat accumulation in the tissues. The food intake of the mutant medaka was higher in post-juveniles and adult stages than that of wild-type (WT) fish. The hyperphagia led to a high growth rate at the post-juvenile stage, but did not to significant alterations in final adult body size. There was no additional deposition of fat in the liver and muscle in the post-juvenile and adult mutants, or in the blood plasma in the adult mutant. However, adult LepR mutants possessed large deposits of visceral fat, unlike in the WT fish, in which there were none. Our analysis confirms that LepR in medaka exert a powerful influence on the control on food intake. Further analyses using the mutant will contribute to a better understanding of the role of leptin in fish. This is the first study to produce fish with leptin receptor deficiency.
authors: Shin-ichi
authors: S
authors: Chisada
authors: Tadahide
authors: T
authors: Kurokawa
authors: Koji
authors: K
authors: Murashita
authors: Ivar
authors: I
authors: Rønnestad
authors: Yoshihito
authors: Y
authors: Taniguchi
authors: Atsushi
authors: A
authors: Toyoda
authors: Yoshiyuki
authors: Y
authors: Sakaki
authors: Shunichi
authors: S
authors: Takeda
authors: Yasutoshi
authors: Y
authors: Yoshiura
mesh_terms: D054369:Agouti-Related Protein / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified / Q000254:growth & development* / Q000378:metabolism; D001066:Appetite / Q000187:drug effects / Q000502:physiology; D001835:Body Weight / Q000187:drug effects*; D004027:Diencephalon / Q000187:drug effects / Q000378:metabolism; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D055786:Gene Knockout Techniques; D006963:Hyperphagia / Q000235:genetics / Q000473:pathology; D050152:Intra-Abdominal Fat / Q000187:drug effects*; D020738:Leptin / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009479:Neuropeptides / Q000494:pharmacology*; D009765:Obesity / Q000378:metabolism; D009990:Oryzias / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D054411:Receptors, Leptin / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D054369:Agouti-Related Protein; D020738:Leptin; D009479:Neuropeptides; D054411:Receptors, Leptin