| Although traditional selection depending on phenotypic value of broiler chicken has made significant improvement in growth rate and meat yield during the past half century, poultry genetics face additional challenges today because of negative correlation between production performance and fitness traits. Accompanying selection for rapid growth, meat-type birds exhibit an increase in physiological disorders such as obesity, ascites, sudden death syndrome, and leg problems, as well as a reduction in overall immunocompetency. Losses in commercial poultry production due to these problems are considerable. Molecular marker-assisted selection (MAS) may required in order to increase selection efficiency and make further improvement in production performance. Genetic markers linked with quantitative trait loci (QTL) allow for direct selection on genotype. The combination of traditional and modern molecular method may be preferred for breeding chicken in the future. Among the genes that are involved with the development of growth and development of fat tissues, PPAR subfamily members are one cluster of the most important genes. The PPARs belong to the nuclear hormone receptor superfamily. Biological effects of PPARs include effects on the absorption, transportation, synthesis and catabolism of fat tissues. The objectives of this study were to investigate the expression of PPARs in various tissue and organs, identify polymorphism of PPARs genes in divergent selection lines for high and low plasma VLDL concentration and local breeds, develop PCR-SSCP methods to detect those DNA polymorphism and evaluate association between polymorphism of these genes and growth and development of body fat traits.The expression level of PPAR genes in specific tissue was analyzed with Northern Blot and half-quantitative RT-PCR. The results showed that the expression pattern of PPAR- a gene in chicken was consistent with rodent and human, it widely expressed in many tissues. Among the investigating tissues and organs, PPAR- a has a high expression in brain, lung, kidney and heart, and a comparative abundance expression in abdominal fat, intestines, stomach and liver. The difference, compared with the rodent and human, was that the expression signal did not detected in muscles The PPAR- Y gene highly expressed only in abdominal far and kidney.PPAR- a gene expressed highly in the liver of newly hatched layer-type birds, following a lower expression in the birds of 2, 4 and 6 weeks of age and high expression in the chicken of 8 weeks of age. Also, the gene has a highexpression in the liver of newly hatched broiler, expressed higher in one day, but declining gradually with age and had a lower expression hi birds of 8 weeks of age. The result indicated that the PPAR- a gene plays an important role in the growth and development of chicken embryo and may have different function in various stages of developing chickens. There were no obvious difference in the expression of PPAR- v gene in abdominal fat between meat-type and layer-type growing birds.The SNPs ( Single Nucleotide Polymorphism) (C/T) were found in exon regions of the PPAR- a and PPAR- y genes, respectively. The genotype detected by PCR-SSCP were defined as AA, AB and BB. Genotype frequency were found to be related with breeds or lines, suggesting that the traits influencing by PPARs, direct or indirectly, have been selected by commercial breeding programs.The PPAR- a polymorphism was associated with abdominal fat (AF) and abdominal fat percentage (AFP), and the BB birds had a higher AF and AFP than AA birds. Combining the characteristics of genotypes distribution in different lines, presumed that the PPAR- a play an important role in chicken fat tissus metabolism . There was no association between PPAR- y polymorphism and body composition traits investigated in this study.The cDNAs of goose PPAR- a and PPAR- V were cloned and sequenced for the first time. The homological comparison analysis among chicken, goose and mammal showed that the identities of both PPAR- a an... |
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