Zhao Xingbo

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.

Genetic polymorphisms of milk epithelial mucin of yaks

Abstract Milk epithelial mucin (MUCI) of yaks was separated by SDS–polyacrylamide gel electrophoresis. Atotal of nine types of MUCI were revealed in 427 yaks from five yak breeds including Maiwa yak, Jiulong yak, Tianzhu white yak, Qinghai yak and Tibetan yak. The molecular weights of MUCI are from 163 kD to 208 kD, most of which are larger than those of bovine. Population genetic analysis shows that the gene frequency and genotype frequency of yak MUCI differ among breeds, with relatively high gene heterozygosity. The five yak breeds studied fall into two groups according to their milk MUCI gene frequency, suggesting that milk MUCI exhibits specificities for local yak groups. * Supported by National Natural Science Foundation of China MUCI and New Century Excellent Talents in University (NCET–04–0135)

Study on the origin and taxonomic status of yak (Poephagus) using cytochrome b gene of mitochondrial DNA

There still exists a remarkable difference on the yak’s taxonomic status in Bovinae. Primers designed according to the mitochondrial gene sequences of Bos taurus reported were used to amplify and sequence the yak’s cytochrome b gene, and the whole sequence of cytochrome b gene was finally obtained. Using Ovis aries as outgroup taxa, the phylogeny about the representative species of Bovinae was analyzed. Results showed that among the different species, the ratio of transition/transversion (Ts/Tv) of Cytochrome b gene was 4.9, suggesting that the mutation was not saturation. The percentage nucleotide sequence divergence between yak and Bovinae was 8.0%–8.6%, which was higher than that of yak and Bison bison. Phylogeny analysis found that Poephagus grunniens and Poephagus mutus clustered first before gathering with Bison bison, indicating higher genetic comparability than that of Bos. The results sustained the idea that Poephagus grunniens and Poephagus mutus shared one ancestor—the primitive yak. The approximate divergence time between these two species was 0.55 million years. The data also supported the viewpoint that the yak is classified into Poephagus of Bovinae, including two species of Poephagus grunniens and Poephagus mutus.