Identificação de polimorfismos no gene da leptina e de seu receptor em duas linhagens de aves e associação com características de desempenho e carcaça / Polymorphism identification in the leptin and leptin receptor gene in two chicken lines and its association with performance and carcass traits

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The trend of industry in producing healthier nourishment, with less fat has raised sensibly. The challenge of animal breeding in the current days is to improve carcass quality of chickens with concomitant reduction in the fat content, witch is a consumers demand. Leptin is a polypeptide hormone secreted mainly by adipocytes with an important role in the regulation of food ingestion, energy metabolism energy and reproduction. The leptin (LEP) and its receptor (LEPR) genes are being subject of intense investigation representing excellent candidate genes for fat deposition in the carcass in marker assisted selection programs. The function of those genes has been intensely studied in mammals, however, in birds few studies were accomplished. The present work aimed to investigate the occurrence of polymorphisms in the LEP and LEPR genes in Chickens, and also evaluate the effects of those polymorphisms on performance and carcass traits. Two chicken lines, a broiler (TT) and a layer line (CC) were used to develop an F2 reference population used in the present study. The reference population was developed in the Poultry Genetic Breeding System at Embrapa Suínos e Aves, in Concórdia/SC. Primers were designed for the PCR amplification of the LEP gene leptina and introns 8 and 19 of the LEPR gene. However, after several attempts it was not possible to amplify the genomic DNA or cDNA of the leptin gene. In the intron 8 of the LEPR gene, SNP C352T was genotyped by DNA sequencing of 247 animals of the F2 population. The T allele was associated with greater carcass yield (P=0,0165), breast yield (P=0,0137), grams of crude protein (P=0,0112) and ashes in the carcass (P=0,0150), while the C allele was associated only to liver yield (0,0102). The SNP G915A in the intron 19 was genotyped by PCR-RFLP of 137 animals from the F2 population, the allele A was associated to the feed intake (P=0,0339), the allele G to the lung yield (P=0,287), and the alleles A and G, when in homozigose, were associated with drumstick and thigh yield (0,0302). Because these SNP are located within an intron area, they are not likely directly involved with the associated characteristics, but they can be linked the other mutation located in the regulatory area of the LEPR gene. In the future other polymorphisms should be explored, in the coding regions of this gene, so they can be used as markers associated to performance and carcass characteristics in poultry. In addition, the LEPR gene was located in the ligation map of the chromosome 8 for the Embrapa population. The next step will be to accomplish the analysis of QTL including the SNPs studied as markers.

ASSUNTO(S)

animals lines hormônios peptidícos genes melhoramento genético animal peptidic hormones carcass linhagens animais broiler layer carcaça animal breeding aves de corte aves poedeiras polimorfismo polymorphism genes

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