| DLK1(delta like non-canonical Notch ligand 1)gene is a paternal-imprinted gene located in the mammalian DLK1-DIO3 imprinting region,also known as the preadipocyte factor 1.DLK1 gene is often used as a marker gene for preadipocytes.Previous studies showed that DLK1 gene can not only promote the growth and development of mammalian muscles,but also inhibit the growth and development of adipose tissue to varying degrees.However,it is unclear whether the differential expression abundance of DLK1 gene in different stages of adipocyte differentiation has a negative regulation on fatty acid synthesis,triglyceride deposition and carcass traits during bovine development.In this study,the regulation of fat metabolism by DLK1 gene was studied on Chinese Simmental steers population and cellular level,which provided a theoretical basis for further analysis of DLK1 function and its application in molecular assisted breeding of beef cattle.In this study,Chinese Simmental steers were used as the research object,and the carcass and meat quality traits of 325 Chinese Simmental cattle were measured.The genetic polymorphism of DLK1 gene was analyzed by sequencing and PCR-RFLP,and DLK1 gene pair was further explored.The relationship between carcass and meat quality traits is aimed at exploring genetic marker-assisted selection from the perspective of genetics to apply to molecular breeding of cattle.To understand the role and regulation mechanism of DLK1 gene on fat anabolism,this study constructed gene overexpression vector pBI-CMV3-DLK1 and pGPU6/GFP/Neo-shRNA interference vector to detect the effect of intracellular triglyceride content in bovine fetal fibroblasts.The role of candidate genes at the cellular level for triglyceride synthesis in the fat metabolism pathway is revealed.The results showed that two SNPs located in the functional region sequence of DLK1 gene,loci I3-478 C>T and I3-609 T>G,were screened in Chinese Simmentalcattle.The correlation analysis between SNPs and carcass traits and fatty acid composition indicated that for I3-478 C>T locus,individuals carrying the homozygous genotype(TT)showed higher sputum weight and kidney fat weight fat coverage rate and waist flesh thickness(p<0.05).Steers with heterozygous genotype(CT)possessed with a higher fat coverage rate and marbling score than CC genotype individuals(p<0.01).For I3-609 T>G locus,individuals with heterozygous genotype(TG)had higher fat coverage rate and perirenal fat weight(p<0.05),steers with GG genotype had higher fat color score than TT genotype individuals(p<0.01).The association analysis between SNPs locus and fatty acid composition showed that the SNP,I3-478 C>T,is significantly correlated with the content of linoleic acid,?-linolenic acid and arachidic acid(p<0.05).The individuals with TT genotype and TG genotype for I3-609 T>G locus had higher content of in linoleic acid,alpha-linolenic acid,arachidic acid and arachidonic acid(p<0.05).These results indicated that the SNPs in the functional region of DLK1 gene were associated with the carcass,meat quality traits and fatty acid composition in Chinese Simmental cattle.DLK1 gene was overexpressed and silenced in bovine fibroblasts respectively to detect the alteration of cellular triglyceride content.The results show that in cells overexpression DLK1 gene,the content of triglyceride was significantly decreased.The amount of triglyceride synthesis in cells had an increasing tendency,when the expression of DLK1 gene is silenced in cells.In summary,SNPs on the functional region of the pre-adipocyte factor DLK1gene: I3-478 C>T and I3-609 T>G are significantly associated to the partial carcass,meat quality traits and intramuscular fatty acid composition of Chinese Simmental steers population.DLK1 gene has a negative regulation on the synthesis of triglycerides in bovine fibroblasts.The results can provide a basis for the further analysis of DLK1 function and the application of DLK1 gene in molecular-assisted breeding of beef cattle. |
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