POMC Gene Expression,Polymorphism And The Association With Reproduction Traits In Chickens

Reproductive trait,which is complexly controlled by many quantitative trait loci(QTLs)and genes,is one of the most important economic traits in the poultry industry.Revealing the genetic effect and molecular mechanism of these genes is beneficial to the selection of reproductive traits in poultry.In this study,Proopiomelanocortin(POMC)was used as a candidate gene for reproductive traits.The single nucleotide polymorphisms(SNPs)of the exons and introns of the POMC gene were detected by direct sequencing in 317 Zhenning yellow chickens,and haplotypes were constructed based on the mutation sites.A general linear model(GLM)program was used to analyze the correlation between each mutation site and the diploid and chicken breeding traits and reproductive hormone levels.At the same time.6 Zhenning yellow chicken hens were selected randomly to detect the POMC gene mRNA level in the heart,liver,spleen,lung,kidney,breast muscle,leg muscle,muscular stomach,glandular stomach,abdominal fat,ovary,hypothalamus,pituitary,brain,primary follicular membrane(FIT),first order granular film(FIG).secondary follicular membrane(F2T)and secondary granular film(F2G),large and white follicle(LWF),small and yellow follicle(SYF)tissues by real-time quantitative PCR.The expression of POMC gene in the pituitary of individuals with different genotypes was detected based on the genotyping results.The experimental results are as follows:1.The results of qPCR showed that there were differences in the expression levels of POMC gene mRNA in different tissues.POMC gene is expressed only in the pituitary,brain,and hypothalamus in chickens.The mRNA expression level is highest in the pituitary.2.The results of POMC gene polymorphism research showed that,2 mutation sites in exon 2(g.1140C>T and g.1185 T>C)and 5 mutation sites(g.2085T>C,g.3566A>C,g.3572G>A,g.3594 G>A,and g.3628G>A)in exon 3 were detected.However,no mutations were detected in exon 1.Each mutation site has three genotypes.The results of the chi-square fitness test showed that all mutation sites were in Hardy-Weinberg equilibrium(P>0.05).The g.1185 T>C,g.3566A>C,g.3572G>A,and g.3628G>A are moderate polymorphisms(0.25<PIC<0.5),and the remaining mutation sites are relatively low and belong to low polymorphism(PIC<0.25).A total of 5 mutation sites were detected in the intron.Among them,there is 1 mutation site on intron 1(g.958G>A)and 4 mutation sites on intron 2(g.1374G>C,g.1393G>A,g.1817C>T and g.1918G>A).Each mutation site has three genotypes.All sites were in Hardy-Weinberg equilibrium(P>0.05).3.Association analysis showed:(1)Chickens with H2H3 diplotypes had higher EW300 and FR than chickens with H1H7(P<0.05)and H3H4 diplotypes(P<0.05).In addition,chickens with the H3H4 diplotypes had the smallest FR among all diplotypes individuals(P<0.Ol).Chickens with H1H5 and H2H2 diplotypes had higher FEHR than chickens with H4H5 diplotypes(P<0.05).(2)g.1140C>T,g.3566A>C,g.3594G>A,and g.3628G>A mutation sites on exons were significantly related to reproductive traits in chickens,while g.1185T>C,G.2085T>C and g.3572G>A mutation sites were not significantly associated with chicken breeding characteristics(P>0.05).Each mutation site on the intron was not significantly associated with E300(P>0.05).Mutations at g.958G>A and g.1817C>T sites were significantly associated with FR,HEHR,and FEHR(P<0.05).(3)There was a significant correlation between the polymorphisms of g.958G>A,g.1393G>A,and g.1817C>T mutation sites and the level of E2(P<0.05).However.there was no significant correlation with other reproductive hormone levels(FSH,LH,and PRL)(P>0.05).4.The result of expression levels of POMC gene in the pituitary of individuals with different genotypes showed that the relative expression of individuals with GC and CC genotype was significantly higher than that of individuals with GG genotype at g.1374G>C mutation site(P<0.05).At g.1393G>A mutation site,the relative expression of individuals with GA genotype was significantly higher than that of individuals with AA genotype(P<0.05).At g.1817C>T mutation site,the relative expression of individuals with CT genotype was significantly higher than that of individuals with CC and TT genotype(P<0.05).At g.1918G>A mutation site,the relative expression of individuals with GG genotype was significantly higher than that of individuals with GA and AA genotypes(P<0.05).In this experiment,the expression profiles of the POMC gene in different tissues of Zhenning yellow chickens were constructed,and the results showed that the highest expression level was in the pituitary.The correlation analysis results showed that the polymorphisms of POMC gene had significant effects on chicken breeding traits,suggesting that it could be used as marker-assisted selection of reproductive traits in chickens.The results above provide theoretical evidence for in-depth revealing of the function and mechanism of POMC gene.