Studies On The Single Nucleotide Polymorphism (SNP) Sites In Melanocortin Receptor-3,-4 Genes And The Relations Between The SNPs And Slaughter & Meat Quality Traits In Chickens

As a member of G -protein coupled receptors (GPCRs), melanocortin receptor (MCR) plays an important role in central melanocortin system (CMS). It functions extensively in the fields of animal nutrition and metabolizing, and influences sebaceous gland excreting, coloring matter sediment and sexual performance. It was approved that the family members MC3R and MC4R function mainly on metabolizing. In human, it was found that MC4R gene is one of the genes whose mutation can result in genetic obesity. In animals, MC3R and MC4R were found having a significant influence on body weight gain and body fat content.240 chickens from 8 populations (including 5 pure lines and 3 crossbreeds developed by Dahen Poultry Breeding Company and Sichuan Animal Science Academy) were studied. All the data on slaughter traits and meat quality traits were gathered. By using single-strand conformation polymorphism (SSCP) method, the single nucleotide polymorphisms (SNPs) sites in MC3R and MC4R genes were detected. Molecular biology and statistic genetics methods were used to predict the conformation changing caused by the mutation of SNPs, and to reveal the association between SNPs and traits. The results were as follows:6 SNPs sites in exons of the 2 genes were determined: MC3R-1424, MC3R-1439, MC4R-662, MC4R-669, MC4R-923 and MC4R-944. The MC4R-669 is all G in chickens of this study, differing from A in the published sequences from Genbank. The single nucleotide mutation G to C of MC4R-662 could cause the translating change from amino acid Gln to His; while the mutation G to A of MC4R-669 could cause the change from Arg to Gly. But there were no changes in the 2 proteins' conformation.The genetic parameters were calculated, and the results showed: MC3R-1424, MC4R-923 and MC4R-944 SNPs sites all had intermediate Polymorphism Information Content (0.25< PIC<0.5). MC3R-1424 PIC =0.367, MC4R-923 PIC =0.349, MC4R-944 PIC =0.367. The X~2 agreement test showed that the population S01xS10 was biased very significantly from Hardy-Weinberg equilibrium at MC3R-1424 SNPs (P<0.01), the population S02 was biased significantly from H-W equilibrium at MC4R-944 SNPs...