Quack leptin

Abstract

BackgroundA LEP transcript up-regulated in lungs of ducks (Anas platyrhynchos) infected by avian influenza A virus was recently described in the Nature Genetics manuscript that reported the duck genome. In vertebrates, LEP gene symbol is reserved for leptin, the key regulator of energy balance in mammals.ResultsLaunching an extensive search for this gene in the genome data that was submitted to the public databases along with duck genome manuscript and extending this search to all avian genomes in the whole-genome shotgun-sequencing database, we were able to report the first identification of coding sequences capable of encoding the full leptin protein precursor in wild birds. Gene structure, synteny and sequence-similarity (up to 54% identity and 68% similarity) to reptilian leptin evident in falcons (Falco peregrinus and cherrug), tits (Pseudopodoces humilis), finches (Taeniopygia guttata) and doves (Columba livia) confirmed that the bird leptin was a true ortholog of its mammalian form. Nevertheless, in duck, like other domestic fowls the LEP gene was not identifiable.ConclusionLack of the LEP gene in poultry suggests that birds that have lost it are particularly suited to domestication. Identification of an intact avian gene for leptin in wild birds might explain in part the evolutionary conservation of its receptor in leptin-less fowls.

Characterization of the Two CART Genes (CART1 and CART2) in Chickens (Gallus gallus)

“…Peripheral administration of leptin to obese mice induces CART mRNA expression, while CART mRNA is almost absent in the arcuate nucleus of leptin-deficient ( ob ) mice or leptin receptor ( fa )-deficient rats [ 5 ]. Recently, the authentic leptin ( ob ) gene has been identified in several birds, including zebra finches and pigeons by our and other laboratories [ 63 – 67 ]. Interestingly, we noted that avian leptin mRNA is predominantly expressed in the brain and pituitary, but undetectable in peripheral tissues including adipose tissue [ 63 ].…”

Comparative omics and feeding manipulations in chicken indicate a shift of the endocrine role of visceral fat towards reproduction

“…Leptin, the key adipokine in the endocrine activity of the fat tissue in mammals, has only recently been identified and characterized in birds [ 15 – 18 ] and its expression was detected in a variety of tissues, but with apparent insignificant expression in the adipose tissue [ 15 , 16 , 18 ]. We also recently identified an additional key adipokine, TNF (also called TNF-α ), previously missing in chicken [ 19 ].…”

Mapping of leptin and its syntenic genes to chicken chromosome 1p

“…In most cases, it is in a tail-to-tail orientation (3′ to 3′; e.g. peregrine falcon, Falco peregrinus [ 23 , 24 ]; fugu, Takifugu rubripes [GenBank Gene ID: 548,631]; green sea turtle, Chelonia mydas [GenBank Gene ID: 102,932,266]; and mouse, Mus musculus [GenBank Gene ID: 16,846]). Moreover, we have previously shown that leptin is very closely linked to RBM28 in peregrine falcon and fugu (1.8 and 0.4 kbp, respectively [ 23 ]).…”

“…peregrine falcon, Falco peregrinus [ 23 , 24 ]; fugu, Takifugu rubripes [GenBank Gene ID: 548,631]; green sea turtle, Chelonia mydas [GenBank Gene ID: 102,932,266]; and mouse, Mus musculus [GenBank Gene ID: 16,846]). Moreover, we have previously shown that leptin is very closely linked to RBM28 in peregrine falcon and fugu (1.8 and 0.4 kbp, respectively [ 23 ]). Since such close proximity and the conserved 3′ to 3′ orientation suggest a local regulation of transcription [ 25 ], we further characterized RBM28 and its expression pattern.…”

“…It is possible that their proximate chromosomal location contributes to their opposing expression pattern. In this respect, it is interesting to note that in the falcon, we have previously demonstrated that leptin and RBM28 are less than 2 kbp apart in a tail-to-tail orientation [ 23 ]. An additional control mechanism could be through the activation of miR-203 by RBM28 [ 36 ], to which the leptin receptor is a potential target [ 38 ].…”