Genetic Variation Of Weaver Gene Association With Milk Traits And Analysis Of Semi-Quantitative In Dairy Goat

The bioinformatics, DNA pool sequencing, PCR-SSCP, PCR-RFLP, CRS-PCR-RFLP, AS-PCR, semi-quantitative PCR and DNA sequence analysis techniques were applied not only to clone and analyze the goat weaver gene, but also to scan the genetic variations of weaver gene and their association with milk trais in 1019 goats, which comprised of four breeds, namely, Xinong Saanen dairy goat (XNSN, n=268), Guanzhong dairy goat (GZ, n=440), Shaanbei white cashmere goat (SBWC, n=196), Xinjiang goat (XJ, n=119).Weaver gene acts in an essential physiological role in the function of many organs, including regulation of insulin secretion by glucose and neurotransmitters. Thus weaver is a potential candidate gene for dairy production. The economic traits comprised of milk yield, fat, protein, solids-not-fat, lactose and total solids percentage. The association between genetic variations and milk traits were analyzed by using general linear model (GLM) or adjusted linear model, as well as population genetic structure and distribution of genotype and allele were calculated by chi-square and quantitative genetic method. These will benefit for the protection, development and application of dairy goat genetic resource, application of DNA marker related to economic traits on marker-assist-selection (MAS), and improvement and promotion of dairy goat. Furthermore, this study contributed to evaluating it as genetic marker in goat breeding, genetics and weaver syndrome.The important results were in the followings:1. Genetic variation of weaver gene and analysis on genetic structure of populationThe varations of seven loci (W1~W7) including weaver gene all five exons, 5'UTR and 3'UTR were studied in 4 populations of goats, namely XNSN, GZ, SBWC and XJWC. In these seven loci, five novel SNPs locating on G5896A, T6256A, C99045T, C99116T and -13A-Indel loci were identified and detected by MluI, AsuII, TaqI, HhaI PCR-RFLP and AS-PCR, respectively.In the MluI analysis, the frequencies of goat MluI-A allele in the analyzed populations were 0.226, 0.248, 0.096 and 0.088 for XNSN, GZ, SBWC and XJWC, respectively. Genotypic frequencies were found to be significantly different in four breeds (χ2=75.842, df=6, P<0.001); In the AsuII analysis, the frequencies of goat AsuII-A allele in the analyzed populations were 0.584, 0.441, 0.073 and 0.063 for XNSN, GZ, SBWC and XJWC, respectively. Genotypic frequencies were found to be significantly different among four breeds (χ2=399.464, df=6, P<0.001). The frequencies of allele MluI-A and AsuII-A in XNSN and GZ populations were significantly higher than those of SBWC and XJWC goats. In the TaqI and HhaI analysis, the frequencies of allele T2 and H2 in Xinong Saanen dairy and Guanzhong dairy populations were significantly greater than those of Shanbei White Cashmere and Xingjiang white cashmere goats, respectively.2. Genetic variations of weaver gene and their effect on milk traitsThe objective of this study was to detect the genetic variation of five loci within weaver gene by PCR-SSCP, DNA sequencing and PCR-RFLP methods in 1,019 Chinese indigenous goats. Association analysis with adjusted milk yield in the XNSN breed indicated that the animals with AsuII-AA genotype owned significantly higher adjusted milk yield than the ones with AsuII-TT genotype in the second lactation (P<0.05). The observation suggested that the allele"AsuII-A"had the positive effects on adjusted milk yield in the second lactation. Association analysis between the SNPs and milk performance traits and growth traits were performed. T2T2 animals had significantly greater milk yield, protein and solids-not-fat percentage than those with the T1T1 genotype (P<0.05). But, no influence of weaver gene variant on milk traits was detected in the HhaI polymorphism locus in the XNSN dairy goat breed. The effect of combined genotype with T6256A and C99045T were not carried out because the r2 of linkage disequilibrium was smaller than 0.33.3. Analysis of semi-quantitative PCR of weaver gene in dairy goatThe expression analysis of semi-quantitative PCR was carry out in different XNSN dairy goat tissues. The result was found that the expressions of the weaver gene were detected in heart, liver, breast, muscle and adipose tissue. Furthermore, the expression was high in heart and liver tissue. And the expression was low in breast, muscle and adipose tissue. High expression group and low expression groups was significantly different (P<0.01). This shows that the weaver gene on the regulation milking is not lactating breast tissue.