title: Identification of the Long-Sought Leptin in Chicken and Duck: Expression Pattern of the Highly GC-Rich Avian leptin Fits an Autocrine/Paracrine Rather Than Endocrine Function.
abstract: More than 20 years after characterization of the key regulator of mammalian energy balance, leptin, we identified the leptin (LEP) genes of chicken (Gallus gallus) and duck (Anas platyrhynchos). The extreme guanine-cytosine content (∼70%), the location in a genomic region with low-complexity repetitive and palindromic sequence elements, the relatively low sequence conservation, and low level of expression have hampered the identification of these genes until now. In vitro-expressed chicken and duck leptins specifically activated signaling through the chicken leptin receptor in cell culture. In situ hybridization demonstrated expression of LEP mRNA in granular and Purkinje cells of the cerebellum, anterior pituitary, and in embryonic limb buds, somites, and branchial arches, suggesting roles in adult brain control of energy balance and during embryonic development. The expression patterns of LEP and the leptin receptor (LEPR) were explored in chicken, duck, and quail (Coturnix japonica) using RNA-sequencing experiments available in the Short Read Archive and by quantitative RT-PCR. In adipose tissue, LEP and LEPR were scarcely transcribed, and the expression level was not correlated to adiposity. Our identification of the leptin genes in chicken and duck genomes resolves a long lasting controversy regarding the existence of leptin genes in these species. This identification was confirmed by sequence and structural similarity, conserved exon-intron boundaries, detection in numerous genomic, and transcriptomic datasets and characterization by PCR, quantitative RT-PCR, in situ hybridization, and bioassays. Our results point to an autocrine/paracrine mode of action for bird leptin instead of being a circulating hormone as in mammals.
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Eyal
authors.initials: E
authors.lastname: Seroussi
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Cinnamon
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Sara
authors.initials: S
authors.lastname: Yosefi
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Olga
authors.initials: O
authors.lastname: Genin
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Julia Gage
authors.initials: JG
authors.lastname: Smith
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Nima
authors.initials: N
authors.lastname: Rafati
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Susanne
authors.initials: S
authors.lastname: Bornelöv
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Leif
authors.initials: L
authors.lastname: Andersson
authors.affiliation: Agricultural Research Organization (E.S., Y.C., S.Y., O.G., J.G.-S., M.F.-E.), Volcani Center, 50250 Bet-Dagan, Israel; Department of Medical Biochemistry and Microbiology (N.R., S.B., L.A.), Uppsala University, SE-75123 Uppsala, Sweden; Department of Animal Breeding and Genetics (L.A.), Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; and Department of Veterinary Integrative Biosciences (L.A.), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458.
authors.forename: Miriam
authors.initials: M
authors.lastname: Friedman-Einat
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D019898:Autocrine Communication / Q000235:genetics*; D001934:Branchial Region / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D002645:Chickens; D003370:Coturnix; D004372:Ducks; D004703:Endocrine System; D005260:Female; D018507:Gene Expression Regulation, Developmental; D057809:HEK293 Cells; D006801:Humans; D017403:In Situ Hybridization; D007668:Kidney / Q000378:metabolism; D020738:Leptin / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018878:Limb Buds / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010053:Ovary / Q000378:metabolism; D019899:Paracrine Communication / Q000235:genetics*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011689:Purkinje Cells / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D054411:Receptors, Leptin / Q000235:genetics* / Q000378:metabolism; D019170:Somites / Q000378:metabolism; D013737:Testis / Q000378:metabolism; D059467:Transcriptome
chemical_list: D020738:Leptin; D012333:RNA, Messenger; D054411:Receptors, Leptin