Analysis Of Genetic Effects Of DKK1 Gene And DKK2 Gene Polymorphisms And Methylation On Growth Traits Of Qianbei Brown Goat

The Wnt signaling pathway is a key signaling pathway that is highly conserved in metazoan cell and can regulate multiple growth stages of animal organisms.The Dickkopf(DKKs)family is a major negative regulator of Wnt signaling pathway and participates in the Wnt pathway cascade by encoding secretory glycoproteins.Dickkopf1(DKK1)and Dickkopf2(DKK2)are important members of the DKKs family.Related studies have shown that DKK1 gene can inhibit osteoblast differentiation,regulate bone formation and bone remodeling,and is an important regulatory factor of bone metabolism;DKK2 gene can affect limb bone and bone density.Therefore,the present study investigated the effects of DNA methylation and SNP of DKK1 gene and DKK2 gene on growth traits from the perspective of molecular genetics and epigenetics,with Qianbei Brown Goat as experimental materials.It aimed to screen for SNPs and DNA methylation sites that significantly influence goat growth traits,which is expected to provide a theoretical basis for molecular breeding of local elite goat breeds.1.Correlation analysis between growth traits and SNPs of DKK1 gene and DKK2 gene in Qianbei Brown GoatSNPs of the DKK1 and DKK2 gene exons and some introns were detected in 123 individuals aged from 4 to 6 months of age(59 male goats and 64 female goats)by constructing DNA pool combined with direct sequencing.Seven SNPs were screened in DKK1 gene,including the first intron C454 T,the third exon T1828 C,the third intron A1911 G,the fourth exon T2056 C,and the fourth exon T2066 C,the fourth Exon G2068 A,the fourth exon T2239 C,in which the fourth exon G2068 A is a missense mutation,resulting in cysteine(Cys)becoming serine(Ser),mutations of other exons are synonymous mutations,1 SNP was screened in DKK2 gene,that is the fourth exon C125904 T.This site mutation did not cause amino acid-encoding changes and was a synonymous mutation.The correlation analysis showed that different genotypes of the first intron C454 T of the DKK1 gene in male goats(♂)were significantly associated with body weight,body length and chest circumference(P<0.05);Different genotypes of the third exon T1828 C of the DKK1 gene in the total population were significantly associated with body height and chest depth(P<0.05),and were significantly associated with body height and chest depth in male goats(♂)(P<0.05);Different genotypes of the third intron A1911 G of the DKK1 gene in female goats(♀)were significantly associated with body length(P<0.05);Different genotypes of the fourth exon T2056 C of the DKK1 gene in the total population、male goats(♂)and female goats(♀)were not significantly associated with body weight,body length,chest depth,chest circumference and girth circumference(P>0.05).Different genotypes of the fourth exon T2066 C of the DKK1 gene in the total population were significantly associated with body weight,body length,chest depth,chest circumference,and girth circumference(P<0.05),and were significantly associated with body height,body length,chest depth,chest circumference and girth circumference in male goats(♂)(P<0.05);Different genotypes of the fourth exon of G2068 A of the DKK1 gene in the total population were significantly associated with body weight,chest depth,chest circumference,and tube circumference(P<0.05),and were significantly associated with body height,chest depth,chest circumference and tube circumference in the male(♂)group(P<0.05).Different genotypes of the fourth exon of T2239 C of the DKK1 gene in the total population were significantly associated with body weight,body height,and chest circumference(P<0.05),and were significantly associated with height in male goats(♂)(P<0.05),and were significantly associated with body weight,chest depth,and chest circumference in female goats(♂)(P<0.05).Different genotypes of the fourth exon C125904 T of the DKK2 gene in the total population、male goats(♂)and female goats(♀)were not significantly associated with body weight,body length,body height,chest circumference,chest depth,chest width,tube circumferenc(P>0.05).2.Genetic effects of methylation of DKK1 and DKK2 gene promoters on growth traits in QianBei Brown goatThe data of blood samples and growth traits of 50 yearling male QianBei Brown goat were collected and screened with statistical software.They were divided into high trait group(H)and low trait group(L),3 in each group,using sequencing technology after bisulfite modification(BSP),exploring the differences in methylation levels between the high and low trait groups of DKK1 and DKK2 genes and the relationship between the methylation status of CpG islands and the growth traits of QianBei Brown goat.The results showed the total methylation rate of CpG islands in the promoter region of DKK1 gene was not significantly different between the high trait group and the low trait group in QianBei Brown goat(P>0.05).The overall methylation degree of CpG islands in the promoter region of DKK1 gene was low between the two groups,but the overall methylation rate of the high trait group was lower than that of the low trait group(P<0.05).The total methylation rate of CpG islands in the promoter region of DKK2 gene was significantly different between the high trait group and the low trait group in QianBei Brown goat(P<0.05),the overall methylation rate of the high trait group was significantly lower than that of the low trait group.The methylation rates of the 5th,10 th,and 12 th CG loci in the target CpG island were significantly different between the high and low trait groups(P<0.05),indicating that the methylation status of the above sites may have effects on the body height 、 body length 、 body height 、 chest circumference,chest depth,chest width,and tube circumference,which can be used as epigenetic marker assisted-selection(eMAS)to improve effective epigenetic marker of growth traits of QianBei Brown goat.