The single nucleotide polymorphisms of chicken melanocortin-4 receptor (MC4R) gene and their association analysis with carcass traits.

Mutations of the melanocortin-4 receptor (MC4R) gene are associated with the appetite, obesity and growth in pig, mice and human. But little is known about the function of chicken MC4R gene. In this study, F2 chicken resource population derived from broilers crossing to Silky was screened for the polymorphisms of the MC4R gene using PCR-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods. Four single nucleotide polymorphisms (SNPs) sites were found. The mutation (C --> T) in the 5' regulation region of chicken MC4R gene results in one more NF-E2 and cap transcription factor binding sites in the mutation allele than in the wild allele. One missense mutation (G --> A) occurs in the coding region (61nt), which changes the glycine to arginine. Moreover, in the coding region there are 2 synonymous mutations, one G --> T mutation at 315nt and one C --> T mutation at 336nt. Least square analysis of the SNPs and carcass traits showed that BB, DD and FF genotypes are significantly associated with body weight, carcass weight (or half carcass weight), and leg muscle weight (P < 0.05 or P < 0.01). But no significant association between the genotypes and abdominal fat weight is found. The results present the evidence that the chicken MC4R gene can be selected as the major candidate gene for the carcass traits such as body weight and growth.