Polymorphisms Of Chicken Hmgcr Gene And Its Association With Serum Vldl Levels And Reproduction Traits

Cholesterol is important for oocyte and embryo development. VLDL is the main carrier of cholesterol in laying hens, which affects the content of cholesterol in oocyte and egg yolk, and HMGCR (HMG-CoA reducase) is the rate-limiting enzyme in the process of cholesterol synthesis. In this experiment,400 Meishan-Wens partridge shank chickens were used to study the concentration of serum VLDL and HMGCR gene polymorphism and its effect on the reproductive traits. Results are as follows:Serum VLDL levels from 384 chickens, according to the concentration, were divided into 4 groups(44-200,200～400,400～600,600～720 mg/ml serum),which corresponding to the egg production were:90.35,105.70,103.65,93.46. Among them, Group 1 and Group 2, Group 3 and Group 4 of the egg production was significantly different (P<0.01), Group 1 and Group 4, Group 2 and Group 3 was not significant (P>0.05); 1,2 serum VLDL concentration and egg production was positively correlated (r=0.51, P<0.01),3,4 serum VLDL concentration and egg production was negatively correlated (r=-0.41, P<0.01).That indicates egg production of moderate concentrations of serum VLDL (VLDL concentration of 200-600mg/ml serum) is higher.3 polymorphic sites were detected by amplified some of HMGCR gene exons and part of intron sequences, using PCR-SSCP method with 6 pairs of primers, which consist of the SNP1 (789bp, G/A) and SNP2 (937bp, C/G) and intron 4 of the SNP3 (2316bp, A/C). These polymorphic Sites were moderately polymorphic (PIC values were 0.3551,0.3204,0.3749).HMGCR gene polymorphisms and association analysis showed that hatching rate of fertilized eggs of different genotypes and young healthy rate of fertilized egg was not significant (P>0.05). In egg production traits:type C_ and D_ in SNP2 was not significant difference (P>0.05); SNP1 and SNP3 of the different genotypes were significantly different (P<0.01), type B_ showed 11.95 eggs higher than type A_, type E_ showed 4.95 eggs higher than type F_. indicating that type B_ and E_ were the dominant genotype for high egg production. The haplotype analysis revealed that the haplotypes in the fertilized egg hatching rate and young healthy rate of fertilized egg was not significant difference(P>0.05), while significant differences in egg production (P<0.01).The best haplotype was BCE (106.11), the worst was haplotype ACE (84.90), a difference of 21.21 eggs,and Greater than the difference between a single site mutation. In a word, haplotypes can increase egg production and more efficient than a single SNP.HMGCR gene polymorphism and serum concentrations of VLDL association analysis:different genotypes of different site were significantly different (P<0.01). Type B_, C_ and E_ with low concentration of serum VLDL, Type A_, D_ and F_with high concentration of serum VLDL, Type A_ than B_, D_ than C_, F_ E_ were higher 214.07,228.99,73.57 (mg/ml serum), respectively, which shows that the three SNP loci of variation was significantly affect serum VLDL concentration. The haplotype analysis revealed that the haplotype differences still reached a significant level (P<0.01).The difference between the highest haplotype ADE (502.12) and the lowest haplotype ACE(184.40) was 317.72 (mg/ml serum), and Greater than the difference between a single site mutation,which showes that haplotypes in the choice of concentrations of serum VLDL choice than the single SNP advantages.During the SNPs analysis,I found that egg production and serum VLDL concentration in ACE haplotypes were the lowest, furtherly evidencing that too-low serum VLDL concentration significantly reduced egg production,so, we should not pursuit too low Cholesterol in fertility traits.Transcription factor binding site analysis:SNP1 variation (G→A) resulted in an increase of transcription factor Oct-1 binding site, CdxA transcription factor binding sites score; and no transcription factor binding sites changes in other two SNP.The results showed that:medium VLDL concentration (200-600mg/ml serum) can be used as candidate indicator of egg production. HMGCR intron SNPs can be used as molecular markers to improve egg production, and thigher efficiency in haplotype than single SNP, especially for BCE haplotypes. Relations between HMGCR gene polymorphisms, serum VLDL levels and the reproductive traits still need further study.