Genome-wide meta-analysis uncovers novel loci influencing circulating leptin levels.

Leptin is an adipocyte-secreted hormone, the circulating levels of which correlate closely with overall adiposity. Although rare mutations in the leptin (LEP) gene are well known to cause leptin deficiency and severe obesity, no common loci regulating circulating leptin levels have been uncovered. Therefore, we performed a genome-wide association study (GWAS) of circulating leptin levels from 32,161 individuals and followed up loci reaching P<10(-6) in 19,979 additional individuals. We identify five loci robustly associated (P<5 × 10(-8)) with leptin levels in/near LEP, SLC32A1, GCKR, CCNL1 and FTO. Although the association of the FTO obesity locus with leptin levels is abolished by adjustment for BMI, associations of the four other loci are independent of adiposity. The GCKR locus was found associated with multiple metabolic traits in previous GWAS and the CCNL1 locus with birth weight. Knockdown experiments in mouse adipose tissue explants show convincing evidence for adipogenin, a regulator of adipocyte differentiation, as the novel causal gene in the SLC32A1 locus influencing leptin levels. Our findings provide novel insights into the regulation of leptin production by adipose tissue and open new avenues for examining the influence of variation in leptin levels on adiposity and metabolic health

Biomechanics and control of vocalization in a non-songbird

The neuromuscular control of vocalization in birds requires complicated and precisely coordinated motor control of the vocal organ (i.e. the syrinx), the respiratory system and upper vocal tract. The biomechanics of the syrinx is very complex and not well understood. In this paper, we aim to unravel the contribution of different control parameters in the coo of the ring dove (Streptopelia risoria) at the syrinx level. We designed and implemented a quantitative biomechanical syrinx model that is driven by physiological control parameters and includes a muscle model. Our simple nonlinear model reproduces the coo, including the inspiratory note, with remarkable accuracy and suggests that harmonic content of song can be controlled by the geometry and rest position of the syrinx. Furthermore, by systematically switching off the control parameters, we demonstrate how they affect amplitude and frequency modulations and generate new experimentally testable hypotheses. Our model suggests that independent control of amplitude and frequency seems not to be possible with the simple syringeal morphology of the ring dove. We speculate that songbirds evolved a syrinx design that uncouples the control of different sound parameters and allows for independent control. This evolutionary key innovation provides an additional explanation for the rapid diversification and speciation of the songbirds

Influência do dimorfismo sexual sobre a morfologia da siringe de galinha d'angola (Numida meleagris) Influence of the sexual dimorphism on the morphology of the syrinx of guinea fowl (Numida meleagris)

Este estudo teve como objetivo realizar uma descrição morfológica e comparativa da siringe, órgão responsável pelo canto das aves, na espécie Numida meleagris. Para isso foram utilizados cinco machos e cinco fêmeas de galinha d'angola, a fim de verificar a sintopia (traquéia, músculos traqueais) e o dimorfismo sexual da siringe. Verificou-se que a siringe se localiza na bifurcação da traquéia e apresenta maior número de cartilagens nos machos. Nos machos, a inserção do músculo traqueal lateral bem como a origem do músculo esterno traqueal localizam-se mais caudalmente e são mais largos em relação às fêmeas. As diferenças existentes entre machos e fêmeas de galinha d'angola revelam a elevada capacidade das fêmeas em produzir sons semelhantes a "tô fraco" enquanto que os machos emitem arrulhos e cacarejos.<br>This study was aimed at making a morphologic and comparative description of the syrinx, the organ that is responsable for the song of the birds in the species Numida meleagris. For that, five males and five females of guinea fowl were used in order to verify the sintopy (trachea, tracheal muscles) and the sexual dimorphism of the syrinx. It was verified that the syrinx is located in the bifurcation of the trachea and it presents larger number of cartilages in the males. The tracheal muscles attaches or origins more caudally in males and both are larger in relation to the females. The existent differences between males and females of Numida meleagris show the high capacity of females in producing sounds how "to fraco" while males emit coo and cackles