| DKKs belong to conservative gene families, whose members DKK1, DKK2and DKK4genes have high sequence homology. They are mainly involved in bone growth and adipocyte differentiation. In recent years, many researches have found that DKKl gene mainly regulates adipocyte differentiation and bone formation, which is the important bone remodeling regulatory factors; DKK2gene plays an important role in limb bone growth and the balance of bone mineral density; DKK4gene is mainly involved in the development of nervous system, and the process of regulating bone formation. Therefore, DKK1, DKK2and DKK4genes for the selection of excellect body measurement and meat quality traits through marker-assisted selection (MAS).In our study, Qinchuan cattle are treated as the research object. Bioinformatics methods and biology software are used to analyze the molecular characterization of DKK1, DKK2and DKK4genes; by DNA sequencing and PCR-SSCP technology, SNPs detection of the three genes are completed; through the application of biometrics software, gene frequency, genetic balance, population genetic and correlation with body measurements and meat quality traits of15SNPs loci were analyzed. Screening functional genes which have important influence on Qinchuan cattle body measurement and meat quality traits is to find effective molecular markers, which will provide a scientific basis for marker-assisted selection of Qinchuan cattle growth traits and breeding with good quality and high yield. The main results of our study are as follwes:1. The molecular characterization of Qinchuan cattle DKK1, DKK2and DKK4genes were predicted and analyzed through bioinformatics. The sequences and amino acid information, the secondary and tertiary structure, signal peptide sequence, transmembrane region, functional domain and subcellular localization of these3proteins were also predicted and analyzed. The phylogenetic tree was also built by comparison with other species and conservative analysis of corresponding proteins in other species. 2. By DNA sequencing and PCR-SSCP technology, SNPs detection in the whole region of DKK1gene, and in the exon regions of DKK2, DKK4genes were completed in experimental Qinchuan cattle populations; and their association with body measurement and meat quality traits was respectively analyzed.(1) SNPs detection in the whole region of DKK1gene was completed in all447tested Qinchuan cattle individuals, we detected seven SNPs. One SNP was detected in the first intron, named G523A. Correlation analysis showed that two marker genotypes were significantly different in RL, IFC (P<0.01), and BL, WH, LMA (P<0.05) at G523A SNP. Four SNPs were detected in the second intron, named A999G、A1169G、G1229A and T1462C, respectively. Correlation analysis showed that three marker genotypes were significantly different in HH, RL, PBW (P<0.01), and BL, WH, BF, IFC (P<0.05) at A999G SNP; three marker genotypes were significantly different in WH, HH, PBW (P<0.01), and BL, BF, IFC (P<0.05) at A1169G SNP; three marker genotypes were significantly different in BL (P<0.05) at G1229A SNP; No significant correlation was observed between three marker genotypes at T1462C SNP for body measerment and meat quality traits. One SNP was detected in the third intron, named C1858T. Correlation analysis showed that three marker genotypes were significantly different in BL, WH, PBW, LMA (P<0.01), and HH, RL (P<0.05) at C1858T SNP. One SNP was detected in the fourth exon, named A2355G, which resulted in a Cys to Arg missense mutation (247th amino acid). Correlation analysis showed that three marker genotypes were significantly different in WH, HH, PBW (P<0.01), and BL, RL, IFC (P<0.05) at A2355G SNP.(2) SNPs detection in the exon regions of DKK2gene were completed in all541tested Qinchuan cattle individuals, we detected three SNPs. Two SNPs were detected in the first exon, named C29T and A164C, respectively. Correlation analysis showed that two marker genotypes were significantly different in PBW, IFC (P<0.01), and BL, RL, BF, LMA (P<0.05) at C29T SNP; two marker genotypes were significantly different in BL, WH, HH, PBW (P<0.01), and BF (P<0.05) at A164C SNP. One SNP was detected in the fourth exon, named C129448A. Correlation analysis showed that three marker genotypes were significantly different in BF (P<0.05) at C129448A SNP.(3) SNPs detection in the exon regions of DKK4gene were completed in all633tested Qinchuan cattle individuals, we detected five SNPs. Two SNPs were detected in the first exon, named G65A and G77T, respectively. Correlation analysis showed that three marker genotypes were significantly different in BL, HW, HG, PBW (P<0.01), and RL (P<0.05) at G65A SNP; three marker genotypes were significantly different in BL (P<0.01), and HH, LMA (P<0.05) at G77T SNP. Two SNPs were detected in the second exon, named C1532G-T1533C, which resulted in a Glu to Arg missense mutation (75th amino acid). Correlation analysis showed that three marker genotypes were significantly different in BL, HH, RL, HW, HG (P<0.01), and BF (P<0.05) at C1532G-T1533C SNPs. One SNP was detected in the third exon, named T2088C, which resulted in a Trp to stop codon nonsense mutation (116th amino acid). Correlation analysis showed that two marker genotypes were significantly different in RL, HG (P<0.01), and HH, BF, LMA (P<0.05) at T2088C SNP. |
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