| The KDM4 family is an important subfamily of lysine-specific demethylase.The KDM4 family affects histone methyl modification by interacting with methylases.These genes are involved in the regulation of chromatin formation,cell development and specific genes transcription by catalyzing the removal of histone methyl modification.At present,the functional study,expression profiles and genetic variations of this family are mainly focused on human and rodents,rarely in livestocks.In this study,the expression profiles of pig KDM4 family genes(KDM4A,KDM4 B,KDM4C,KDM4D)among different tissues were explored,the genetic variations of these four genes were verified,and the association analysis between genetic variations and reproductive traits were detected.These analyses results provide a theoretical basis for the subsequent marker-assisted selection breeding.The main results of this thesis are as follows:1.Tissue expression profiles of KDM4 family genesThe tissue expression profiles of KDM4 family genes were carried on ten different tissues from three 2-week-old piglets and three 3-month-old piglets.Meanwhile,testis tissues from three 9-month-old pigs were harvested.Relative expression of KDM4 family genes in porcine testes at 3 different ages were detected.The results showed that at2-week-old stage,except for KDM4 D,the KDM4 family genes were expressed in various tissues of pigs.At 3-month-old stage,the expression of KDM4 family genes in several tissues was extremely low.Intriguingly,the KDM4 family genes were highly expressed in liver at all detected developmental stages.Additionally,with the development of testis,the KDM4 C and KDM4 D expression levels were significantly changed,indicating that these two genes may regulate testis development and can be used as potential candidate genes for molecular marker identification.2.Association analysis between single nucleotide polymorphism(SNP)within the KDM4 D gene and reproductive traitsPCR-RFLP was used to detect the genetic polymorphism of KDM4 D gene in 442 Yorkshire and Landrace pigs,and two SNP mutations were detected.The g.1078A>G locus is located in the region of the Jmj N domain,and the g.1358G>C locus is located in the first extron.Besides,the g.1078A>G is a missense mutation(Pro > Ser)and g.1358G>C is a synonymous mutation.Through association analysis,the g.1358G>C locus was significantly associated with testis long circumference(TLC),testicular short circumference(TSC)and testicular weight(TW)(P < 0.05).Meanwhile,the individuals with AA and AG genotype had better phenotype than individuals with GG genotype.However,the g.1078A>G locus was not associated with TLC,TSC and TW.Linkage disequilibrium analysis showed that there were no linkages between these two SNP loci.Protein tertiary structure prediction revealed that the g.1358G>C site altered the protein tertiary structure of the Jmj N domain.3.Association analysis between insertion-deletion(In Del)within the KDM4 C gene and reproductive traitsThe two indel loci,16 bp indel(rs789224950)and 9 bp indel(rs1112990890),were detected from 442 Yorkshire and Landrace pigs.Association analysis results revealed that the16 bp indel locus was significantly associated with TW(P < 0.05)in 15-day-old Yorkshire piglets.Meanwhile,the individuals with ID genotype had greater TW than individuals with DD genotype.However,the 9 bp indel locus was associated with none of TLC,TSC and TW.In summary,this study verified the expression profile of KDM4 family genes in pigs,and detected two molecular markers which had significant impacts on boar reproductive capacity.All the data provides a theoretical basis for the subsequent marker-assisted selection breeding of boars. |
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