Polymorphism In C-X-C Motif Chemokine Receptor 2 Gene (CXCR2) By PCR-RFLP And Its Association With Somatic Cell Score In Chinese Holstein

Chemokine receptor 2(CXCR2)activate signal transduction pathways for neutrophil migrating,immune and inflammatory responses.In this study,246 Chinese Holstein dairy cows were used to study for genetic variation of CXCR2 gene in promoter,intron,exon and3-terminal non-coding regions by using PCR-RFLP,DNA sequencing technology and DNA sequence analysis combined with SSPS analysis,in order to explore the genetic structure and genetic information diversity of CXCR2 gene in experimental cattle population.The genetic mutation loci in CXCR2 gene were correlated with milk production traits based on individual milk production traits including milk yield,quantity of milk fat,protein and somatic cell score(SCS).Molecular markers affecting on milk production and disease resistance traits were screened for marker-assisted selection,high-quality and new-yield breeding of economic traits of Chinese Holstein dairy cows.The study was found following results:1.The genetic variation of CXCR2 gene in Chinese Holstein dairy cattle was studied by PCR-RFLP and sequencing.Three genetic variation loci of CXCR2 gene were screened out in experimental cattle populations,encoded as g.106178917 A>G;g.106186215G>A and g.106191980 A>G.Further DNA sequence analysis showed that the mutations of g.106178917 A>G;g.106186215 G>A and g.106191980 A>G were located in the intron of the bovine CXCR2 gene.2.The genetic analysis of polymorphic loci showed that the dominant allele A of g.106178917 A>G locus was 59.15%and the highest frequency of AG genotype was79.27%.The dominant G allele at g.106186215G>A locus was 96.55%,and the frequency of GG genotype was 93.91%.The dominant allele A of g.106191980 A>G locus was54.37%,and the highest frequency of AG genotype was 89.58%.The calculation of x~2 test showed that three genetic variation loci in the CXCR2 gene sequence were in Hardy Weinberg non-equilibrium state in the cattle population.The results of PIC analysis showed that G.106178917 A>G and g.106191980 A>G were in intermediate polymorphism,while g.106186215 G>A was in low polymorphism.3.The results of association analysis showed that three genetic variation loci in CXCR2gene sequence were significantly correlated with milk yield.Among them,AG genotype at g.106178917 A>G locus,AA genotype at g.106186215 G>A locus and AG genotype at g.106191980 A>G locus were significantly correlated with high milk yield.Three genetic variation sites were identified in the intron of the CXCR2 gene in Chinese Holstein cows,and all showed a highly significant correlation with the SCS,milk yield,fat and protein percentage of dairy cows,indicating that these three SNPs locus can be used as a molecular marker gene for milk traits and disease resistance traits of Chinese Holstein cows.