Investigation of Leptin gene in broiler and layer chicken lines

Abstract

Leptin, a polypeptide hormone secreted mainly by adipose tissue, plays an important role in feed intake regulation, energy metabolism and reproduction in several species. Its function has been intensively studied in mammals; however, in birds limited information is available. The cDNA sequence for chicken leptin has been reported, and high hepatic expression levels of leptin were associated with fat deposition in selected bird lines. However, controversies still remain concerning to the chicken leptin gene and several authors failed to amplify this gene from genomic DNA or cDNA. In view of this controversy and the importance of this gene, the present study aimed to investigate the leptin gene in a population of birds developed by Embrapa Swine and Poultry Research Center (Brazil). First of all, the sequences of Gallus gallus leptin gene (GenBank AF012727) and Mus musculus (GenBank NM_008493) were aligned with the objective of designing primers in conserved regions among the two species, since 94.6% of similarity is described in the literature in those species. For all four pairs of primers designed, several amplification tests were performed with both DNA and cDNA, but neither unique fragment nor expected band size was ever achieved. The leptin sequence in GenBank does not represent the sequence of the chicken leptin gene.

Leptin in farm animals: where are we and where can we go?

“…The gene sequence reported for chicken (Taouis et al, 1998;Ashwell et al, 1999) was disputed by Friedman-Einat et al (1999) and by Burt (2004) but Richards et al (2000) used antibody to 15-aa of pig leptin to identify leptin protein in chicken plasma, fat and liver while Neglia et al (2008) showed it in chicken gut. However, Ninov et al (2008) could not amplify any of three primers deduced from Genbank AFO12727 or another from Dridi et al (2005a). Low nucleotide sequence homology between species need not mean radically different proteins, e.g.…”

Circulating leptin levels do not reflect the amount of body fat in the dunlin Calidris alpina during migration

“…Despite reports of cloning and sequencing leptin gene in birds (Taouis et al, 1998;Ashwell et al, 1999a), some researchers failed to confirm its existence (Friedman-Einat et al, 1999;Ninov et al, 2008;Yosefi et al, 2010) and deny leptin expression in these vertebrates. Additionally, the controversy concerns very high similarity (97%) in nucleotide sequence between chicken and mouse leptin (Taouis et al, 1998), which is very unlikely from an evolutionary point of view.…”

Niveles de leptina sérica en aves comerciales

“…Se conoce que la secuencia del gen de leptina en aves es 94.6% similar a la secuencia del gen leptina en ratones (Ninov et al, 2008), pero tiene un residuo de cisteína adicional que pueda afectar su estructura conformacional (Taouis et al, 1998;Ashwel et al, 1999). Así mismo, en el pollo se detectó exclusivamente la expresión de la leptina en el hígado, característica atribuible al metabolismo lipídico en el hígado que es el órgano principal de la lipogénesis en las aves (Ninov et al, 2008).…”

“…Se conoce que la secuencia del gen de leptina en aves es 94.6% similar a la secuencia del gen leptina en ratones (Ninov et al, 2008), pero tiene un residuo de cisteína adicional que pueda afectar su estructura conformacional (Taouis et al, 1998;Ashwel et al, 1999). Así mismo, en el pollo se detectó exclusivamente la expresión de la leptina en el hígado, característica atribuible al metabolismo lipídico en el hígado que es el órgano principal de la lipogénesis en las aves (Ninov et al, 2008). Por otro lado, se sabe que la insulina, la corticosterona y los estrógenos en el pollo regulan esta expresión en el hígado, especie que además, tiene un crecimiento muy rápido, lo que conlleva a un exceso de grasa corporal, generando problemas en el desarrollo muscular y mortalidad (Taouis et al, 2001).…”