Application Of Mxd3 Genetic Markers To Select Growth Traits In Three Indigenous Cattle Breeds

Maximum dimeric protein 3（Mxd3） is a special member of the Mad family. The reseach have been reported that Mxd3 gene in obese people and zebrafish expression levels were increased. And then the researchers used knockout Mxd3 gene in 3T3-L1 cell line artificial feeding excess food（diet-induced） obesity type mouse visceral fat cell growth will be inhibited, indicating that Mxd3 genes may play an important role in fat metabolism, it can be inferred Mxd3 regulate growth and development as a candidate gene. To date, there have been few reports on bovine Mxd3. In order to get some molecular markers for beef cattle breeding program, we detected SNPs of bovine Mxd3 and analyzed the association between SNPs and growth traits. So as to increase our understanding of the physiological role of bovine Mxd3 1. Genetic variation in Mxd3DNA pooling and forced PCR-RFLP were used for bovine Mxd3 gene sequencing of three Chinese cattle breeds, including Qinchuan cattle, Jinnan cattle and Jiaxian cattle, in a total of 696 individuals. Three novel SV1（AC₀00164: g.2231T>C）,SV2（AC₀00164: g.3338T>C）, SV3（AC₀00164: g.5800A>G） and one insertion 16 bp of Mxd3 were detected according to the sequencing results. Among these variants, SV1（AC₀00164: g.2231 T>C）and the insertion+16bp were located at intron 4. The SV2（AC₀00164: g.3338T>C）and SV3（AC₀00164: g.5800A>G）locus was located at intron 5 and exon 7 which resulted in a silent mutation, respectively.The results of the population genetic showed that the were moderate polymorphism in three of the four locus（0.25<PIC<0.5）The linkage disequilibrium and haplotypes were analysed as well. The results shown that Hap3 was the highest frequency in each of the three cattle.These differences might be partly attributed to the variations of genetic background and selection pressure. 2. Polymorphism of Mxd3 gene and the association with growth traitsThe association analysis about the single locus in Mxd3 gene with the growth traits were showed that in the three ingenious cattle SV1（ AC₀00164: g.2231T>C） site was significantly associated with chest circumference and chest depth in Qinchuan cattle, but it was significantly associated with the cannon circumference and body weight in Jiaxian cattle; the SV2（AC₀00164: g.3338T>C）was only significantly associated with the cannon circumference in Jiaxian; SV3（AC₀00164: g.5800A>G） significantly associated with Qinchuan chest circumference and body weight, and only significant associated with body length of Jiaxian; while we found all the sites were connection with Jinnan cattle and the SV4 site was also no relevant with growth traits of three Chinese cattle breeds.The combined genotype of the Mxd3 gene and growth traits in Qinchuan correlation analysis found that body length, chest and body weight was significantly associated with growth traits Qinchuan, and growth traits Qinchuan chest deep and significant correlation. Which combined genotypes CCTCGADW was the dominant genotype. In conclution the Mxd3 gene could be used as molecular markers in early marker assisted selection. In this study, we combined the technologies with the genetic variation of Mxd3, Put forward theoretical application of Mxd3 gene in molecular breeding of indigenous cattle and to achieve the purpose of combining the experiments and practice and make a foundation of cattle breeding and development.